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revision 1.2 by wakaba, Mon Jul 16 08:38:48 2007 UTC revision 1.41 by wakaba, Sun Sep 21 05:09:35 2008 UTC
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1  <!DOCTYPE html><html id="error-description" lang="en" xmlns:d="http://suika.fam.cx/~wakaba/archive/2007/wdcc-desc/" xmlns="http://www.w3.org/1999/xhtml">  <!DOCTYPE html><html id="error-description" lang="en" xmlns:d="http://suika.fam.cx/~wakaba/archive/2007/wdcc-desc/" xmlns="http://www.w3.org/1999/xhtml">
2  <head>  <head>
3  <title xml:lang="en">Description of Errors —  <base href="cc/">
4  Web Document Conformance Checker (BETA)</title>  
5  <link href="cc-style" rel="stylesheet">  
6    <link href="../cc-style" rel="stylesheet">
7  <link href="#license" rel="license">  <link href="#license" rel="license">
8  </head>  <title xml:lang="en">Description of Errors — WebHACC (β)</title></head>
9  <body>  <body>
10  <h1>Description of Errors</h1>  <header>
11    <h1><a href="../cc-about"><abbr title="Web Hypertext Application Conformance Checker (β)"><img alt="WebHACC" src="../icons/title"></abbr></a></h1>
12    <h2>Description of Errors</h2>
13    </header>
14    
15    
16    
17    <div class="section" id="WebHACC:Heading"><h3>
18        
19      </h3>
20        <p><a href="./#input"><abbr title="Web Hypertext Application Conformance Checker">WebHACC</abbr></a>
21        is a <em>conformance checker</em> (or validator) for Web documents,
22        supporting <a href="../standards">latest Web standards</a> including
23        <a href="http://whatwg.org/html5"><abbr title="Hypertext Markup Language">HTML</abbr>5</a>,
24        <a href="urn:ietf:rfc:4287">Atom 1.0</a>,
25        <a href="http://www.w3.org/Style/CSS/current-work"><abbr title="Cascading Style Sheets">CSS</abbr>3</a>.</p>
26    
27        <p><strong><a href="./#input">Check your document</a></strong>, or
28        <a href="../cc-about">learn more about
29        <abbr title="Web Hypertext Application Conformance Checker">WebHACC</abbr></a>.</p>
30      </div>
31    
32    <section id="character-encoding-layer">
33    <h2>Character Encoding Layer Errors</h2>
34    
35    <div class="section" id="fallback-char-error"><h3>Octet sequence <code><var>{octets}</var></code>
36      is not an allowed representation of the character
37      <code><var>{char}</var></code> — character reference
38      <code><var>{char:hexref}</var></code> should be used instead.</h3></div>
39    
40    <div class="section" id="fallback-unassigned-error"><h3>No character is assigned to octet sequence
41      <code><var>{octets}</var></code>.</h3></div>
42    
43    <div class="section" id="illegal-octets-error"><h3>Octet sequence <code><var>{octets}</var></code>
44      is illegal.</h3></div>
45    
46    <div class="section" id="invalid-state-error"><h3>The input stream is broken.</h3>
47        <p>The input stream is encoded in <code>ISO-2022-JP</code>
48        or its variant but is partially broken.</p>
49    
50        <p>Note that an <code>ISO-2022-JP</code> stream must end in the ASCII
51        state.</p>
52      </div>
53    
54    <div class="section" id="unassigned-code-point-error"><h3>No character is assigned to octet sequence
55      <code><var>{octets}</var></code>.</h3></div>
56    </section>
57    
58    <section id="html5-character-encoding">
59    <h2>HTML5 Character Encoding Errors</h2>
60    
61    <div class="section" id="charset:not-supported"><h3>Character encoding <code><var>{value}</var></code>
62      is not supported and the explicit character encoding specification is
63      ignored.  The result of the conformance checking might be
64      <em>wrong</em>.</h3></div>
65    
66    <div class="section" id="disallowed-character-encoding"><h3>Character encoding <code><var>{text}</var></code>
67      is not allowed for <abbr>HTML</abbr> document.</h3>
68        <p>The character encoding used for the document is not allowed
69        for <abbr>HTML</abbr> document.  The document is non‐conforming.</p>
70      </div>
71    
72    <div class="section" id="bad-character-encoding"><h3>Character encoding <code><var>{text}</var></code>
73      should not be used for <abbr>HTML</abbr> document.</h3>
74        <p>The character encoding used for the document is not recommended
75        for <abbr>HTML</abbr> document.  The document is non‐conforming
76        unless there is any good reason to use that encoding.</p>
77      </div>
78    
79    <div class="section" id="non-utf-8-character-encoding"><h3>Use of UTF-8 is encouraged (this document
80      is encoded in <code><var>{text}</var></code>).</h3>
81        <p>Use of UTF-8 as the character encoding of the document is encouraged,
82        though the use of another character encoding is still conforming.</p>
83      </div>
84    
85    <div class="section" id="character-encoding-unchecked"><h3>Conformance for character encoding requirements
86      cannot be checked, since the input is not a byte stream.</h3>
87        <p>The conformance checker cannot detect whether the input document
88        met the requirements on character encoding, since the document
89        is not inputed as a serialized byte sequence.  The document is
90        not conforming if it is not encoded in an appropriate character
91        encoding with appropriate labeling.</p>
92      </div>
93    
94    <div class="section" id="no-character-encoding-declaration"><h3>There is no character encoding
95      declaration.</h3>
96        <p>The document does not contain a character encoding
97        declaration.  Unless the character encoding is explicitly
98        specified in lower‐level protocol, e.g. in <abbr>HTTP</abbr>,
99        or is implied by <abbr>BOM</abbr>, there must be a character
100        encoding declaration.  The document is non‐conforming.</p>
101    
102        <p>The long character encoding declaration syntax
103        <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"&gt;</code>
104        is obsolete.  The new syntax is:</p>
105        <pre class="html example">
106    <code>&lt;meta charset="<var>charset-name</var>"&gt;</code></pre>
107    
108        <p>Note that the <code>encoding</code> declaration in <abbr>XML</abbr>
109        declaration has no effect for <abbr>HTML</abbr> document.</p>
110      </div>
111    
112    <div class="section" id="non-ascii-superset"><h3>No character encoding metadata is found
113      in lower‐level protocol nor is there <abbr>BOM</abbr>, while
114      character encoding <code><var>{text}</var></code>
115      is not a superset of <abbr>ASCII</abbr>.</h3>
116        <p>The document is not labeled with character encoding name
117        in lower‐level protocol, e.g. in <abbr>HTTP</abbr>, and
118        the document is not begin with <abbr>BOM</abbr>.  In addition,
119        the character encoding of the document is not a superset of
120        <abbr>ASCII</abbr>.  The document is non‐conforming.</p>
121    
122        <p>Unless there is a <abbr>BOM</abbr>, the character encoding
123        for the document must be specified in e.g. <abbr>HTTP</abbr>‐level,
124        as:</p>
125        <pre class="http example">
126    <code>Content-Type: text/html; charset=<var>charset-name</var></code></pre>
127    
128        <p>Existence of <abbr>HTML</abbr> character encoding declaration, i.e.
129        <code class="html example">&lt;meta charset="<var>charset-name</var>"&gt;</code>,
130        does not allow to omit <code>charset</code> parameter
131        for <abbr>HTML</abbr> document encoded in non‐<abbr>ASCII</abbr>
132        compatible encoding.</p>
133    
134        <p>Character encodings <code>Shift_JIS</code>, <code>Windows-31J</code>,
135        and <code>ISO-2022-JP</code> are <em>not</em> a superset of
136        <abbr>ASCII</abbr> for the purpose of <abbr>HTML</abbr> conformance.</p>
137      </div>
138    
139    <div class="section" id="sniffing:chardet"><h3>Character encoding of this document is sniffed
140      as <code><var>{text}</var></code> (Sniffed because no explicit specification
141      for the character encoding of this document is found in the transfer
142      procotol headers).</h3></div>
143    
144    <div class="section" id="sniffing:default"><h3>Character encoding of this document is defaulted
145      to <code><var>{text}</var></code> because no explicit specification
146      for the character encoding of this document is found in the transfer
147      procotol headers.</h3></div>
148    
149    <div class="section" id="chardecode:fallback"><h3>Results might be <em>wrong</em>, since the
150      conformance checker cannot find an appropriate decoder for the character
151      encoding used for the document.</h3>
152        <p>The conformance checker cannot find an appropriate decoder for
153        the character encoding used to encode characters in the document.</p>
154    
155        <p>This error is raised if:</p>
156        <ul>
157        <li>the conformance checker cannot find any decoder for the character
158        encoding in use, but it knows that the encoding is similar to another
159        character encoding, such that it uses the decoder for that character
160        encoding, and therefore some octets might be interpreted incorrectly,
161        or,</li>
162        <li>the conformance checker find a decoder for the character encoding
163        in use, but it does not know whether the decoder is conforming to the
164        relevant specification or not, and therefore some octets might be
165        interpreted incorrectly.</li>
166        </ul>
167    
168        <p>In either case, the result shown by the conformance checker might
169        contain wrong errors caused by errorneous decoder or might not contain
170        errors that should be raised if an appropriate decoder is used.</p>
171    
172        <!-- TODO: add advise that either install relevant modules or
173             join the developmenet of the modules... -->
174      </div>
175    
176    <div class="section" id="chardecode:no-error"><h3>Conformance error checking for the character
177      encoding <code><var>{text}</var></code> is not supported.</h3></div>
178    
179    <div class="section" id="charset-label:matching"><h3>Sniffed character encoding
180      <code><var>{text}</var></code> is same as the character encoding specified
181      in the character encoding declaration.  This is <em>not</em> an
182      error.</h3></div>
183    
184    <div class="section" id="charset-label-detected"><h3>While parsing the document as
185      <code><var>{text}</var></code>, a character encoding declaration specifying
186      a different character encoding is found.  The document
187      is reparsed.</h3>
188        <p>While parsing a document in a character encoding,
189        a character encoding declaration which declares the character
190        encoding of the document as another character encoding is found.
191        The occurence of this warning itself does not make the document
192        non‐conforming.  However, the failure of the first attempt to
193        to detect the character encoding might be a result of non‐conformance
194        of the document.</p>
195    
196        <p>The document will be reparsed from the beginning.  Some error
197        or warning might be reported again.</p>
198    
199        <p>These are suggestions to avoid this warning:</p>
200        <ul>
201        <li>Specify <code>charset</code> parameter in the <code>Content-Type</code>
202        field in the <abbr>HTTP</abbr> header, as:
203        <pre class="HTTP example">
204    <code>Content-Type: text/html; charset="<var>charset-name</var>"</code></pre></li>
205        <li>Put the character encoding declaration
206        (<code class="html example">&lt;meta charset="<var>charset-name</var>"&gt;</code>)
207        just after <code class="html example">&lt;head&gt;</code> start tag.</li>
208        <li>Use <code>UTF-8</code>.</li>
209        </ul>
210      </div>
211    </section>
212    
213    <section id="character-set-layer">
214    <h2>Coded Character Set Layer Errors</h2>
215    
216    <div class="section" id="NULL"><h3>The <code class="charname">NULL</code> character
217      is not allowed.</h3></div>
218    
219    <div class="section" id="control-char"><h3>Code point <code><var>{text}</var></code> is
220      not allowed.</h3></div>
221    
222    <div class="section" id="nonchar"><h3>Noncharacter <code><var>{text}</var></code>
223      is found in the input stream.</h3>
224        <p>Noncharacter code points are used in the input stream.</p>
225    
226        <p>Noncharacter code points are reserved for internal processings.
227        Their use for information interchanges are forbidden.</p>
228    
229        <p>In addition, they are not allowed in HTML document.</p>
230        <!-- "permanently undefined Unicode characters" in HTML5. -->
231      </div>
232    
233    <div class="section" id="non-unicode"><h3>Character <code><var>{text}</var></code> is not
234      a Unicode character.</h3></div>
235    
236    <div class="section" id="unicode-deprecated"><h3>Use of character <code><var>{text}</var></code>
237      is deprecated.</h3></div>
238    
239    <div class="section" id="unicode-discouraged"><h3>Use of character <code><var>{text}</var></code>
240      is discouraged.</h3></div>
241    
242    <div class="section" id="unicode-not-preferred"><h3>Code point <code><var>{text}</var></code>
243      is not the preferred representation of that character.</h3></div>
244    
245    <div class="section" id="unicode-should"><h3>Character <code><var>{text}</var></code>
246      should not be used in many cases.</h3></div>
247    
248    </section>
249    
250  <section id="html5-tokenize-error">  <section id="html5-tokenize-error">
251  <h2>HTML5 Parse Errors in Tokenization Stage</h2>  <h2>HTML5 Parse Errors in Tokenization Stage</h2>
252    
253  <div class="section tokenize-error" id="duplicate-attribute"><h3>There are two attributes with same name.</h3>  <div class="section" id="bad-attribute-name"><h3>Attribute name cannot contain characters
254      <p>Attributes must be unique in an element.  Specifying    <code>"</code>, <code>'</code>, and <code>=</code>.</h3></div>
255      attributes with same name more than once is non-conforming.</p>  
256    <div class="section" id="bad-attribute-value"><h3>Attribute value must be quoted by <code>"</code>
257      or <code>'</code> if it contains a <code>"</code>, <code>'</code>, or
258      <code>=</code> character.</h3>
259        <p>In an unquoted attribute value, a character <code>"</code>
260        (<code>U+0022</code> <code class="charname">QUOTATION MARK</code>),
261        <code>'</code> (<code>U+0026</code>
262        <code class="charname">APOSTROPHE</code>), or <code>=</code>
263        (<code>U+003D</code> <code class="charname">EQUAL SIGN</code>)
264        is contained.  These characters are not allowed in unquoted attribute
265        values, since they are used to quote attribute values or to separate
266        attribute name and value.</p>
267    
268        <p>This error is also raised if one try to use empty attribute
269        value like <code class="html bad example">&lt;foo bar= baz=&gt;</code>;
270        in this example, <code class="html bad example">baz=</code> is
271        treated as an invalid attribute value for the attribute
272        <code class="html bad example">bar</code>, not as another attribute.</p>
273      </div>
274    
275    <div class="section" id="bare-ero"><h3>The <code>&amp;</code> character must
276      be escaped as <code class="html example">&amp;amp;</code>.</h3>
277        <p>An <code>&amp;</code> character which
278        is not part of any reference appears in the input stream.
279        The document is non‐conforming.</p>
280    
281        <p><em>Any <code>&amp;</code> character in URI (or IRI)
282        must be escaped as <code class="example">&amp;amp;</code>.</em></p>
283    
284        <p>The <code>&amp;</code> character must
285        be the first character of a reference:
286          <dl class="switch">
287          <dt>Named entity reference</dt>
288              <dd><pre class="html example">
289    <code>&amp;<var>entity-name</var>;</code></pre>
290              where <var>entity-name</var> is the name of the
291              character entity to be referenced.</dd>
292          <dt>Numeric character reference</dt>
293              <dd><pre class="html example">
294    <code>&amp;#<var>d</var>;</code></pre>
295              where <var>d</var> is the decimal representation of
296              the code position of the character to be referenced.</dd>
297          <dt>Hexadecimal character reference</dt>
298              <dd><pre class="html example">
299    <code>&amp;#x<var>h</var>;</code></pre>
300              where <var>h</var> is the hexadecimal representation
301              of the code position of the character to be referenced.</dd>
302          </dl>
303        </p>
304    
305        <p>To represent <code>&amp;</code> as a data character, use
306        named entity reference:
307          <pre class="html example">
308    <code>&amp;amp;</code></pre>
309        </p>
310      </div>
311    
312    <div class="section" id="bare-etago"><h3>A <code>&lt;/</code> string is not followed
313      by a tag name.</h3>
314        <p>There is a <code>&lt;</code> (<code>U+003C</code>
315        <code class="charname">LESS-THAN SIGN</code>) character
316        immediately followed by a <code>/</code> (<code>U+005F</code>
317        <code>SOLIDUS</code>) character, which is not part
318        of any end tag, in the input stream.  The document
319        is non-conforming.</p>
320    
321        <p>The <code>&lt;/</code> sequence immediately followed
322        by an <abbr title="End of file pseudo-character">EOF</abbr> is
323        interpreted as a string data of <code>&lt;/</code>.</p>
324    
325        <p>The <code>&lt;/</code> sequence as string data must
326        be escaped as:
327        <pre class="html example">
328    <code>&amp;lt;/</code></pre>
329        </p>
330      </div>
331    
332    <div class="section" id="bare-stago"><h3>A <code>&lt;</code> character is not followed
333      by tag name or by a <code>!</code> character.</h3>
334        <p>A <code>&lt;</code> (<code>U+003C</code>
335        <code class="charname">LESS-THAN SIGN</code>) character which is not part
336        of any markup appears in the input stream.</p>
337    
338        <p>The <code>&lt;</code> character as a data character must
339        be escaped as:
340        <pre class="html example">
341    <code>&amp;lt;</code></pre>
342        </p>
343      </div>
344    
345    <div class="section" id="bare-nero"><h3>The decimal representation of the code position
346      of a character must be specified after <code>&amp;#</code>.</h3>
347        <p>An <code>&amp;</code> (<code>U+0026</code>
348        <code class="charname">AMPERSAND</code>) character immediately
349        followed by a <code>#</code> (<code>U+0023</code>
350        <code>NUMBER SIGN</code>) character which
351        is not part of any reference appears in the input stream.
352        The document is non-conforming.</p>
353    
354        <p>The string <code>&amp;#</code> must be the first two characters
355        of a reference:
356          <dl class="switch">
357          <dt>Numeric character reference</dt>
358              <dd><pre class="html example">
359    <code>&amp;#<var>d</var>;</code></pre>
360              where <var>d</var> is the decimal representation of
361              the code point of the character to be referenced.</dd>
362          <dt>Hexadecimal character reference</dt>
363              <dd><pre class="html example">
364    <code>&amp;#x<var>h</var>;</code></pre>
365              where <var>h</var> is the hexadecimal representation
366              of the code point of the character to be referenced.</dd>
367          </dl>
368        </p>
369    
370        <p>To represent <code>&amp;#</code> as data characters, use
371        a named entity reference for the <code>&amp;</code> character:
372          <pre class="html example">
373    <code>&amp;amp;#</code></pre>
374        </p>
375      </div>
376    
377    <div class="section" id="bare-hcro"><h3>The hexadecimal representation of the code position
378      of a character must be specified after <code>&amp;#x</code>.</h3>
379       <p>The string <code>&amp;#x</code> or <code>&amp;#X</code> which
380       is not part of any reference appears in the input stream.
381        The document is non-conforming.</p>
382    
383        <p>The string <code>&amp;#x</code> or <code>&amp;#X</code> must
384        be the first three characters of a hexadecimal reference:
385          <pre class="html example">
386    <code>&amp;#x<var>h</var>;</code></pre>
387        where <var>h</var> is the hexadecimal representation
388        of the code point of the character to be referenced.</p>
389    
390        <p>To represent <code>&amp;#x</code> as data characters, use
391        a named entity reference for the <code>&amp;</code> character:
392          <pre class="html example">
393    <code>&amp;amp;#x</code></pre>
394        </p>
395      </div>
396    
397    <div class="section" id="bogus-comment"><h3>String <code>&lt;!</code> is not followed
398      by <code>--</code>.</h3>
399        <p>There is a <code>&lt;</code> (<code>U+003C</code>
400        <code class="charname">LESS-THAN SIGN</code>) character
401        followed by a <code>!</code> (<code>U+0021</code>
402        <code class="charname">EXCLAMATION MARK</code>) character,
403        which is not followed by a <code>--</code> or
404        <code>!DOCTYPE</code>.  The document is non-conforming.</p>
405    
406        <dl class="switch">
407        <dt>Comments</dt>
408          <dd>In HTML document, comments must be introduced by
409          <code class="example">&lt;!--</code> (<code>&lt;!</code>
410          <em>immediately</em> followed
411          by <em>two</em> <code>-</code>s) and must be terminated by
412          <code class="example">--&gt;</code>.
413          Strings <code>&lt;!</code> not followed
414          by <code>--</code> and <code>&lt;!-</code> not followed by
415          <code>-</code> are not valid open delimiters for comments.</dd>
416        <dt>Marked sections, including <code>CDATA</code> sections</dt>
417          <dd>Marked sections are not allowed in HTML document.</dd>
418        <dt>Markup declarations</dt>
419          <dd>Markup declarations, except for <code>DOCTYPE</code>
420          and comment declarations, are not allowed in HTML document.</dd>
421        <dt>String <code>&lt;!</code></dt>
422          <dd>String <code>&lt;!</code> must be escaped as
423          <code class="example">&amp;lt;!</code>.</dd>
424        </dl>
425      </div>
426    
427    <div class="section" id="bogus-end-tag"><h3>String <code>&lt;/</code> is not followed
428      by tag name.</h3>
429        <p>There is a <code>&lt;</code> (<code>U+003C</code>
430        <code class="charname">LESS-THAN SIGN</code>) character
431        immediately followed by a <code>/</code> (<code>U+005F</code>
432        <code>SOLIDUS</code>) character, which is not part
433        of any end tag, in the input stream.  The document
434        is non-conforming.</p>
435    
436        <p>The <code>&lt;/</code> sequence not followed by a
437        tag name is parsed as an opening of bogus comment.</p>
438    
439        <p>The <code>&lt;/</code> sequence as string data must
440        be escaped as:
441        <pre class="html example">
442    <code>&amp;lt;/</code></pre>
443        </p>
444      </div>
445    
446    <div class="section" id="C1-character-reference"><h3>Character reference to
447      <code><var>{text}</var></code> is not allowed.</h3></div>
448    
449    <div class="section" id="CR-character-reference"><h3>Character reference to
450      <code>U+000D</code> (<code class="charname">CARRIAGE RETURN</code>)
451      is not allowed.</h3></div>
452    
453    <div class="section" id="dash-in-comment"><h3>There is a <code>--</code> sequence
454      in a comment.</h3>
455        <p>There is a <code>-</code> (<code>U+002D</code>
456        <code class="charname">HYPHEN-MINUS</code>) character
457        at the end of the comment or a <code>--</code> sequence
458        in the comment.  The document is non-conforming.</p>
459    
460        <p>Comments cannot contain a string <code>--</code>, as in XML.
461        Unlike SGML, there cannot be more than one comments
462        (where <i>comment</i> is an SGML term) in the comment
463        declaration.</p>
464      </div>
465    
466    <div class="section" id="duplicate-attribute"><h3>There are two attributes with name
467          <code><var>{text}</var></code>.</h3>
468        <p>There are more than one attributes with the same
469        name in a tag.  The document is non-conforming.</p>
470    
471      <p>The <code>motion</code> attribute is not part of the HTML standard.      <p>The <code>motion</code> attribute is not part of the HTML standard.
472      Use <code>img</code> element with animation GIF instead.</p>      Use <code>img</code> element with animation GIF instead.</p>
473    </div>    </div>
474    
475  <div class="section tokenize-error" id="nestc"><h3>Void element syntax (<code>/&gt;</code>) cannot be  <div class="section" id="empty-start-tag"><h3>Empty start tag (<code>&lt;&gt;</code>) is not
476      allowed.</h3></div>
477    
478    <div class="section" id="empty-end-tag"><h3>Empty end tag (<code>&lt;/&gt;</code>) is not
479      allowed.</h3></div>
480    
481    <div class="section" id="end-tag-attribute"><h3>End tag cannot have attributes.</h3></div>
482    
483    <div class="section" id="empty-unquoted-attribute-value"><h3>Attribute value is not specified.</h3>
484        <p>The attribute value is not specified after the <code>=</code>
485        (<code>U+003C</code> <code class="charname">EQUAL SIGN</code>)
486        character.</p>
487    
488        <p>When an attribute value is empty, the <code>=</code> character after
489        the attribute name must be specified as:</p>
490    
491        <p><code class="html example">&lt;foo bar&gt;</code></p>
492    
493        <p>Instead, quotation marks can be used to explicitly represent that
494        the attribute value is empty, as:</p>
495    
496        <p><code class="html example">&lt;foo bar=""&gt;</code></p>
497    
498        <p>... or like:</p>
499    
500        <p><code class="html example">&lt;foo bar=''&gt;</code></p>
501      </div>
502    
503    <div class="section" id="invalid-character-reference"><h3>Character reference to
504      <code><var>{text}</var></code> is not allowed.</h3></div>
505    
506    <div class="section" id="nestc"><h3>Polytheistic slash (<code>/&gt;</code>) cannot be
507    used for this element.</h3>    used for this element.</h3>
508      <p>The void element syntax <code>/&gt;</code> syntax can only be      <p>Polytheistic slash (<code>/&gt;</code>) must not be used
509        for the element.  The document is non-conforming.</p>
510    
511        <p>The polytheistic slash can only be
512      used for <code>base</code>, <code>link</code>, <code>meta</code>,      used for <code>base</code>, <code>link</code>, <code>meta</code>,
513      <code>hr</code>, <code>br</code>, <code>img</code>,      <code>hr</code>, <code>br</code>, <code>img</code>,
514      <code>embed</code>, <code>param</code>, <code>area</code>,      <code>embed</code>, <code>param</code>, <code>area</code>,
515      <code>col</code>, and <code>input</code> elements.      <code>col</code>, and <code>input</code> elements.</p>
     For any other elements, using that syntax is non-conforming.</p>  
516    
517      <p>Unlike XML, the void element syntax (<code>/&gt;</code>) has      <dl class="switch">
518        <dt><code>&lt;script/&gt;</code></dt>
519            <dd><p>The polytheistic slash cannot be used for <code>script</code>
520            element.  Even for an empty <code>script</code> element,
521            there must be an explicit end tag
522            <code class="html example">&lt;/script&gt;</code>.</p>
523    
524            <p><strong>NOTE</strong>: Though some user agents interpret
525            polytheistic slash for <code>script</code> element as the
526            closing of the element, such usage is not allowed under
527            the current standard.</p></dd>
528        <dt><code>&lt;basefont/&gt;</code>, <code>&lt;bgsound/&gt;</code>,
529        <code>&lt;frame/&gt;</code>, <code>&lt;keygen/&gt;</code>,
530        <code>&lt;spacer/&gt;</code>, <code>&lt;wbr/&gt;</code></dt>
531            <dd>These elements are themselves non-conforming.</dd>
532        <!-- isindex, image -->
533        <dt><code>&lt;command/&gt;</code>, <code>&lt;event-source/&gt;</code>,
534        <code>&lt;nest/&gt;</code>, or <code>&lt;source/&gt;</code></dt>
535            <dd>Future revision of HTML5 parsing algorithm is expected
536            to allow polytheistic slash for these elements.</dd>
537        <dt><code>&lt;a/&gt;</code>, <code>&lt;p/&gt;</code></dt>
538            <dd>These elements are not always empty and therefore
539            polytheistic slash is not allowed.  Use explicit end tag
540            to represent empty element as:
541              <pre class="example html">
542    <code>&lt;p&gt;&lt;/p&gt;</code></pre>
543            </dd>
544        </dl>
545    
546        <p>Note that, unlike in XML, the polytheistic slash has
547      no effect in HTML.</p>      no effect in HTML.</p>
548    </div>    </div>
549    
550    <div class="section" id="no-DOCTYPE-name"><h3>After the string <code>&lt;!DOCTYPE </code>, the
551      document type name must be specified.</h3></div>
552    
553    <div class="section" id="no-PUBLIC-literal"><h3>After the keyword <code>PUBLIC</code>, no
554      oublic identifier is specified.</h3></div>
555    
556    <div class="section" id="no-refc"><h3>Character reference must be closed by a
557      <code>;</code> character.</h3></div>
558    
559    <div class="section" id="no-space-before-DOCTYPE-name"><h3>After the string <code>&lt;!DOCTYPE</code>, there
560      must be at least a white space character before the document type
561      name.</h3></div>
562    
563    <div class="section" id="no-space-between-attributes"><h3>Attributes must be separeted by at least a
564      white space character.</h3></div>
565    
566    <div class="section" id="no-SYSTEM-literal"><h3>After the keyword <code>SYSTEM</code>, no
567      system identifier is specified.</h3></div>
568    
569    <div class="section" id="pio"><h3>Processing instruction
570      (<code>&lt;?<var>...</var>&gt;</code>) is not allowed in HTML
571      document.</h3>
572        <p>Processing instructions (<code>&lt;?<var>...</var>?&gt;</code>),
573        including XML declaration (<code>&lt;?xml <var>...</var>?&gt;</code>)
574        and XML style sheet <abbr title="processing instruction">PI</abbr>
575        (<code>&lt;?xml-stylesheet <var>...</var>?&gt;</code>), are not allowed
576        in the HTML syntax.  The document is non-conforming.</p>
577    
578        <dl class="switch">
579        <dt><code>&lt;?xbl?&gt;</code> (<abbr>XBL</abbr> Association)</dt>
580          <dd>An <abbr>XBL</abbr> binding cannot be associated by
581          <abbr title="processing instruction">PI</abbr> in <abbr>HTML</abbr>
582          document.  Use <code>binding</code> property in <abbr>CSS</abbr>
583          style sheet as:
584            <pre class="html example">
585    <code>&lt;style&gt;
586    p {
587      binding: url(binding.xbl);
588    }
589    &lt;/style&gt;</code></pre>
590          </dd>
591        <dt><code>&lt;?xml?&gt;</code> (XML declaration)</dt>
592            <dd>XML declaration is unnecessary for HTML documents.</dd>
593        <dt><code>&lt;?xml-stylesheet?&gt;</code> (XML style sheet
594        <abbr title="processing instruction">PI</abbr>)</dt>
595            <dd>Use HTML <code>link</code> element with <code>rel</code>
596            attribute set to <code>stylesheet</code> (or,
597            <code>alternate stylesheet</code> for an alternate style
598            sheet).
599              <pre class="example html">
600    <code>&lt;link rel=stylesheet href="path/to/stylesheet.css"&gt;</code></pre>
601            </dd>
602        <dt><code>&lt;?php?&gt;</code> or
603        <code>&lt;? <var>... <abbr>PHP</abbr> code ...</var> ?&gt;</code>
604        (<abbr>PHP</abbr> code)</dt>
605            <dd>The conformance checker does <em>not</em> support
606            checking for PHP source documents.</dd>
607        <dt>Other processing instructions</dt>
608            <dd>Processing instructions cannot be inserted in an HTML
609            document.  Use XML document or insert
610            <code>ProcessingInstruction</code> node by scripting.</dd>
611        </dl>
612    
613        <p>Web browsers will parse processing instructions as bogus
614        comments.  Some legacy Web browsers, such as IE:mac and
615        some mobile Web browsers, will display processing instructions
616        as string.</p>
617      </div>
618    
619    <div class="section" id="string-after-DOCTYPE-name"><h3>There is a bogus string after the document type
620      name.</h3></div>
621    
622    <div class="section" id="string-after-PUBLIC"><h3>There is a bogus string after the keyword
623      <code>PUBLIC</code>.</h3></div>
624    
625    <div class="section" id="string-after-PUBLIC-literal"><h3>There is a bogus string after the public
626      identifier.</h3></div>
627    
628    <div class="section" id="string-after-SYSTEM"><h3>There is a bogus string after the keyword
629      <code>SYSTEM</code>.</h3></div>
630    
631    <div class="section" id="string-after-SYSTEM-literal"><h3>There is a bogus string after the system
632      identifier.</h3></div>
633    
634    <div class="section" id="unclosed-attribute-value"><h3>Attribute value is not closed by a quotation
635      mark.</h3></div>
636    
637    <div class="section" id="unclosed-comment"><h3>Comment is not closed by a string
638      <code>--&gt;</code>.</h3></div>
639    
640    <div class="section" id="unclosed-DOCTYPE"><h3>The <code>DOCTYPE</code> is not closed by a
641      <code>&gt;</code> character.</h3></div>
642    
643    <div class="section" id="unclosed-PUBLIC-literal"><h3>The public identifier literal is not closed by a
644      quotation mark.</h3></div>
645    
646    <div class="section" id="unclosed-SYSTEM-literal"><h3>The system identifier literal is not closed by a
647      quotation mark.</h3></div>
648    
649    <div class="section" id="unclosed-tag"><h3>Tag is not closed by a <code>&gt;</code>
650      character.</h3></div>
651    
652  </section>  </section>
653    
654  <section id="html5-parse-errors">  <section id="html5-parse-errors">
655  <h2>HTML5 Parse Errors in Tree Construction Stage</h2>  <h2>HTML5 Parse Errors in Tree Construction Stage</h2>
656    
657  <div class="section parse-error" id="after-head"><h3>The <code><var>$0</var></code> element cannot be  <div class="section" id="after-after-frameset"><h3>There is a start tag
658    inserted between <code>head</code> and <code>body</code> elements.</h3>    <code>&lt;<var>{text}</var>&gt;</code> is after the <code>html</code> element
659      <p>A start tag occurs after the <code>head</code> element is closed    is closed.</h3></div>
660    
661    <div class="section" id="after-after-frameset:/"><h3>There is an end tag
662      <code>&lt;/<var>{text}</var>&gt;</code> is after the <code>html</code> element
663      is closed.</h3></div>
664    
665    <div class="section" id="after-body"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code> is
666      not allowed after the <code>body</code> is closed.</h3></div>
667    
668    <div class="section" id="after-body:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code> is
669      not allowed after the <code>body</code> is closed.</h3></div>
670    
671    <div class="section" id="after-body:#text"><h3>Non‐white‐space characters are not allowed
672      after the <code>body</code> is closed.</h3></div>
673    
674    <div class="section" id="after-frameset"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code> is
675      not allowed after the <code>frameset</code> is closed.</h3></div>
676    
677    <div class="section" id="after-frameset:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code> is
678      not allowed after the <code>frameset</code> is closed.</h3></div>
679    
680    <div class="section" id="after-frameset:#text"><h3>Non‐white‐space characters are not allowed
681      after the <code>frame</code> is closed.</h3></div>
682    
683    <div class="section" id="after-head"><h3>The <code><var>{text}</var></code> element cannot be
684      inserted between <code>head</code> and <code>body</code>
685      elements.</h3>
686        <p>A start tag appears after the <code>head</code> element is closed
687      but before the <code>body</code> element is opened.      but before the <code>body</code> element is opened.
688      The document is non-conforming.</p>      The document is non-conforming.</p>
689    </div>    </div>
690    
691  <div class="section parse-error" id="no-DOCTYPE"><h3>This document does not start with the  <div class="section" id="after-html"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code> is
692    <code>DOCTYPE</code> declaration.</h3></div>    not allowed after the <code>html</code> is closed.</h3>
693        <p>The start tag of an element appears after the
694        <code>body</code> element has been closed.  The document is
695        non-conforming.</p>
696    
697        <p>Any content of the document other than <code>head</code>
698        contents and comments must be put into the <code>body</code>
699        element.</p>
700      </div>
701    
702    <div class="section" id="after-html:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code> is
703      not allowed after the <code>html</code> is closed.</h3>
704        <p>The end tag of an element appears after the
705        <code>body</code> element has been closed.  The document is
706        non-conforming.</p>
707    
708        <p>Any content of the document other than <code>head</code>
709        contents and comments must be put into the <code>body</code>
710        element.</p>
711      </div>
712    
713    <div class="section" id="after-html:#text"><h3>Non‐white‐space characters are not allowed
714      after the <code>html</code> is closed.</h3></div>
715    
716    <div class="section" id="image"><h3>The <code>image</code> element is
717      obsolete.</h3></div>
718    
719    <div class="section" id="in-a:a"><h3>Anchor cannot be nested.</h3>
720        <p>HTML <code>a</code> elements cannot be nested.
721        The document is non-conforming.</p>
722    
723        <p>In the HTML syntax, a start tag of the <code>a</code>
724        implies the end tag of any opening <code>a</code> element.</p>
725      </div>
726    
727    <div class="section" id="in-body"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code>
728      is not allowed in the <code>body</code> element.</h3>
729        <p>The start or end tag of an element, which
730        cannot be a descendant of <code>body</code> element, appears
731        in the input stream while the <code>body</code> element has been opened.
732        The document is non-conforming.</p>
733      </div>
734    
735    <div class="section" id="in-body:#eof"><h3>Some element is not closed before the end of
736      file.</h3></div>
737    
738    <div class="section" id="in-button:button"><h3>The <code>button</code> element cannot be
739      nested.</h3></div>
740    
741    <div class="section" id="in-CDATA:#eof"><h3>Element is not closed before the end of
742      file.</h3></div>
743    
744    <div class="section" id="in-form:form"><h3>Start tag <code>&lt;form&gt;</code> is
745      not allowed in a <code>form</code> element.</h3></div>
746    
747    <div class="section" id="in-frameset"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code> is
748      not allowed in a <code>framset</code> element.</h3></div>
749    
750    <div class="section" id="in-frameset:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code> is
751      not allowed in a <code>frameset</code> element.</h3></div>
752    
753    <div class="section" id="in-frameset:#text"><h3>Non‐white‐space characters are not allowed
754      in a <code>frameset</code> element.</h3></div>
755    
756    <div class="section" id="in-head:head"><h3>Start tag <code>&lt;head&gt;</code>
757      is not allowed in the <code>head</code> element.</h3>
758        <p>There is a start tag <code>&lt;head&gt;</code> in the
759        <code>&lt;head&gt;</code> element.  The document is non-conforming.</p>
760    
761        <p>In an HTML document there must not be more than
762        one <code>head</code> element, therefore no more than one
763        start tag <code>&lt;head&gt;</code> can appear in the input stream.</p>
764      </div>
765    
766    <div class="section" id="in-html:#DOCTYPE"><h3>A <code>DOCTYPE</code> appears after any
767      element or data character has been seen.</h3>
768        <p>A <code>DOCTYPE</code> appears after any element or data character
769        has been seen.  The document is non-conforming.</p>
770        
771        <p>The <code>DOCTYPE</code> must be placed before any
772        tag, reference, or data character.  Only white space characters
773        and comments can be inserted before the <code>DOCTYPE</code>.</p>
774      </div>
775    
776    <div class="section" id="in-nobr:nobr"><h3>The <code>nobr</code> element cannot be
777      nested.</h3></div>
778    
779    <div class="section" id="in-noscript"><h3>The <code><var>{text}</var></code> element is not
780      allowed in a <code>noscript</code> element in the
781      <code>head</code> element.</h3></div>
782    
783    <div class="section" id="in-noscript:/"><h3>An end tag <code>&lt;/<var>{text}</var>&gt;</code>
784      appers before the <code>noscript</code> element is closed.</h3></div>
785    
786    <div class="section" id="in-noscript:#eof"><h3>A <code>noscript</code> element is not closed
787      before the end of file.</h3></div>
788    
789    <div class="section" id="in-noscript:#text"><h3>Non‐white‐space characters are not allowed
790      in a <code>noscript</code> element in the <code>head</code>
791      element.</h3></div>
792    
793    <div class="section" id="in-PCDATA:#eof"><h3>Element is not closed before the end of
794      file.</h3></div>
795    
796    <div class="section" id="in-select"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code>
797      is not allowed in a <code>select</code> element.</h3></div>
798    
799    <div class="section" id="in-select:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code>
800      is not allowed in a <code>select</code> element.</h3></div>
801    
802    <div class="section" id="in-table"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code>
803      is not allowed in a <code>table</code> element.</h3>
804        <p>The start or end tag of an element, which
805        cannot be a child of <code>table</code> element, appears
806        in the input stream while the <code>table</code> element has been opened
807        but no other element has been opened.  The document is non-conforming.</p>
808    
809        <p>In <code>table</code>, only table related elements
810        are allowed; any other element must be contained in
811        <code>td</code> or <code>th</code> element to form
812        a part of the table, or <code>caption</code> element to create
813        a table caption.</p>
814      </div>
815    
816    <div class="section" id="in-table:/"><h3>End tag <code>&lt;/<var>{text}</var>&gt;</code>
817      is not allowed in a <code>table</code> element.</h3></div>
818    
819    <div class="section" id="in-table:#text"><h3>Non‐white‐space character is not allowed within
820      the <code>table</code> element, outside of the caption and cells.</h3>
821        <p>A non‐white‐space character appears in <code>table</code>.
822        The document is non-conforming.</p>
823    
824        <p>In <code>table</code>, only table related elements
825        are allowed; any other element and data character must be contained in
826        <code>td</code> or <code>th</code> element to form
827        a part of the table, or <code>caption</code> element to create
828        a table caption.</p>
829      </div>
830    
831    <div class="section" id="isindex"><h3>The <code>isindex</code> element is
832      obsolete.</h3></div>
833    
834    <div class="section" id="missing-start-tag:tr"><h3>Start tag of <code>tr</code>
835      element is missing.</h3>
836        <p>Start tag of a <code>tr</code> element, which is <em>not</em>
837        optional, is missing.  The document is non-conforming.</p>
838    
839        <p>In a table section, a <code>&lt;tr&gt;</code> start tag
840        must occur before any <code>&lt;td&gt;</code> or
841        <code>&lt;th&gt;</code> start tag.  Though the HTML5 parser
842        implies the <code>&lt;tr&gt;</code> start tag before
843        these start tags, it must be explicitly specified.</p>
844      </div>
845    
846    <div class="section" id="no-DOCTYPE"><h3>This document does not start with a
847      <code>DOCTYPE</code>.</h3>
848        <p>The document does not start with a <code>DOCTYPE</code>.
849        The document is non-conforming.</p>
850    
851  <div class="section parse-error" id="not-closed"><h3>Element <code><var>$0</var></code> is not      <p>An HTML document must start by a <code>DOCTYPE</code>:
852    closed.</h3></div>        <pre class="html example">
853    <code>&lt;!DOCTYPE HTML&gt;</code></pre>
854        </p>
855    
856  <div class="section parse-error" id="not-HTML5"><h3>This document is written in an old version of      <p>Only white space characters and comments are allowed
857    HTML.</h3></div>      before the <code>DOCTYPE</code>.  XML declaration is <em>not</em>
858        allowed in HTML document.</p>
859      </div>
860    
861    <div class="section" id="not-closed"><h3>Element <code><var>{text}</var></code> is not
862      closed.</h3>
863        <p>End tag of an element is not found before, for example,
864        an end tag of another element appears or
865        the end of the document.  The document is non-conforming.</p>
866    
867        <p>Only <code>body</code>, <code>colgroup</code>, <code>dd</code>,
868        <code>dt</code>, <code>head</code>, <code>html</code>, <code>li</code>,
869        <code>ol</code>, <code>option</code>, <code>optgroup</code>,
870        <code>p</code>, <code>rb</code>, <code>rp</code>, <code>rt</code>,
871        <code>tbody</code>, <code>td</code>, <code>tfoot</code>,
872        <code>th</code>, <code>thead</code>, <code>tr</code>,
873        <code>ul</code> end tag can be omitted in HTML documents.
874        For any element except for void element, there must be an explicit
875        end tag.</p>
876    
877        <dl class="switch">
878        <dt>HTML <code>canvas</code> element</dt>
879          <dd>Though the element is void in earlier versions of Safari,
880          the <code>canvas</code> element is <em>no</em> longer
881          defined as empty.  There must be an end tag
882          <code class="html example">&lt;/canvas&gt;</code>.</dd>
883        </dl>
884    
885        <p>Note that misnesting tags, such as
886        <code class="bad example">&lt;a&gt;&lt;b&gt;&lt;/a&gt;&lt;/b&gt;</code>, are not
887        allowed and they also cause this error.</p>
888      </div>
889    
890    <div class="section" id="not-first-start-tag"><h3>This <code>&lt;html&gt;</code> tag is not
891      the first start tag.</h3>
892        <p>There is a start tag of the <code>html</code> element
893        that it not the first start tag in the input stream.
894        The document is non-conforming.</p>
895    
896        <p>In an HTML document, there cannot be more than one
897        <code>html</code> element and therefore there cannot be
898        more than one <code>&lt;html&gt;</code> tag.  In addition,
899        nothing can be placed before the <code>&lt;html&gt;</code> tag
900        except a <code>DOCTYPE</code>, white space characters,
901        and comments.</p>
902      </div>
903    
904    <div class="section" id="not-HTML5"><h3>This document is written in an old version of
905      HTML.</h3>
906        <p>The document contains a <code>DOCTYPE</code> declaration
907        that is different from HTML5 <code>DOCTYPE</code> (i.e.
908        <code class="example html">&lt;!DOCTYPE HTML&gt;</code>).
909        The document is non‐conforming.</p>
910    
911        <p>The document might or might not be conformant to
912        some version of HTML.  However, conformance to any HTML
913        specification other than HTML5 provides for no practical
914        convenience, since Web borwsers will parse any
915        HTML document (roughly) as defined in HTML5.</p>
916      </div>
917    
918    <div class="section" id="start-tag-not-allowed"><h3>Start tag <code>&lt;<var>{text}</var>&gt;</code> is
919      not allowed here.</h3></div>
920    
921    <div class="section" id="unmatched-end-tag"><h3>Element <code><var>{text}</var></code> is not
922      opened.</h3>
923        <p>An end tag appears though no element with the same name
924        has been opened.  The document is non-conforming.</p>
925    
926        <p>For any end tag in HTML document, there must be a
927        corresponding start tag.</p>
928    
929        <dl class="switch">
930        <dt>HTML <code>base</code>, <code>basefont</code>,
931        <code>bgsound</code>, <code>br</code>, <code>col</code>,
932        <code>embed</code>, <code>frame</code>, <code>hr</code>,
933        <code>image</code>, <code>img</code>, <code>input</code>,
934        <code>isindex</code>, <code>link</code>, <code>meta</code>,
935        <code>param</code>, <code>spacer</code>, or <code>wbr</code> element</dt>
936          <dd>End tag is not allowed for these elements, since
937          those content must always be empty.  Remove end tag.</dd>
938        <!-- keygen -->
939        <!-- command, event-source, nest, source -->
940        </dl>
941      </div>
942    
943  <div class="section parse-error" id="unmatched-end-tag"><h3>Element <code><var>$0</var></code> is not  <div class="section" id="XSLT-compat"><h3>The <code>DOCTYPE</code> legacy string is
944    opened.</h3></div>    used.</h3>
945        <p>The <code>DOCTYPE</code> with the <code>DOCTYPE</code> legacy
946        string, i.e.
947        <code class="html bad example">&lt;!DOCTYPE HTML PUBLIC "XSLT-compat"&gt;</code>
948        is used.</p>
949    
950        <p>The <code>DOCTYPE</code> legacy string should not be used for documents
951        <em>not</em> generated from XSLT transformation process.  It is allowed
952        only to enable to use XSLT style sheets with the HTML output mode, which
953        does not support generation of the <code>DOCTYPE</code> with no
954        <code>PUBLIC</code>
955        identifier.  For other purposes, the <code>DOCTYPE</code> legacy
956        string, i.e. <code class="html bad example">PUBLIC "XSLT-compat"</code>,
957        is useless and should not be used.</p>
958      </div>
959    
960  </section>  </section>
961    
962  <section id="element-content-model-errors">  <section id="element-content-model-errors">
963  <h2>Element Content Model Errors</h2>  <h2>Element Content Model Errors</h2>
964    
965  <div class="section content-model-error" id="character-not-allowed"><h3>Data character is not allowed in this  <div class="section" id="basehref-after-URL-attribute"><h3>The <code>base</code> element with the
966      <code>href</code> attribute specified cannot be placed after
967      any attribute with a URL.</h3></div>
968    
969    <div class="section" id="basetarget-after-hyperlink"><h3>The <code>base</code> element with the
970      <code>target</code> attribute specified cannot be placed after
971      any element that defines a hyperlink.</h3></div>
972    
973    <div class="section" id="character-not-allowed"><h3>Data character is not allowed in this
974    context.</h3>    context.</h3>
975      <p>A data character occurs where it is not allowed in this      <p>A data character appears where it is not allowed in this
976      context.  The document is non-conforming.</p>      context.  The document is non-conforming.</p>
977    
978      <p>Possible causes:      <p>Possible causes:
979        <dl>        <ul>
980        <dt>If the erred element is an inline-level element (such        <li><p>A data character cannot be a child
981        as <code>a</code> or <code>span</code>)</dt>        of certain sectioning elements such as <code>body</code>,
982            <dd><p>A data character cannot be a child        <code>section</code>, and <code>blockquote</code>.</p>
983            of certain sectioning elements such as <code>body</code>,  
984            <code>section</code>, and <code>blockquote</code>.</p>        <p>Any inline-level content must be put
985          in e.g. paragraph element such as <code>p</code>.</p></li>
986            <p>Any inline-level content must be put        <li><p>Though some elements such as <code>div</code>,
987            in e.g. paragraph element such as <code>p</code>.</p></dd>        <code>li</code>, and <code>td</code> allow
988        <dt>If the erred element is a block-level element (such as        <em>either one</em> of block-level or inline-level content
989        <code>div</code> or <code>h<var>n</var></code>)</dt>        is allowed.  If there is a block-level content,
990            <dd><p>Though some elements such as <code>div</code>,        any inline-level content must be put
991            <code>li</code>, and <code>td</code> allow        in e.g. paragraph element such as <code>p</code>.</p></li>
992            <em>either one</em> of block-level or inline-level content        </ul>
           is allowed.  If there is a block-level content,  
           any inline-level content must be put  
           in e.g. paragraph element such as <code>p</code>.</p></dd>  
       </dl>  
993      </p>      </p>
994    </div>    </div>
995    
996  <div class="section content-model-error" id="child-element-missing"><h3>There must be a <code><var>$0</var></code>  <div class="section" id="character-not-allowed:empty"><h3>Non‐white‐space characters are not allowed in
997    element as a child of this element.</h3>    an empty element.</h3></div>
998    
999    <div class="section" id="character-not-allowed:atom|PersonConstruct"><h3>Non‐white‐space characters are not allowed in
1000      Person construct.</h3></div>
1001    
1002    <div class="section" id="character-not-allowed:atom|TextConstruct"><h3>Non‐white‐space characters are not allowed in
1003      Text construct.</h3></div>
1004    
1005    <div class="section" id="child-element-missing"><h3>There must be an element
1006      <code><var>{text}</var></code> as a child of this element.</h3>
1007      <p>The content model of the element is so defined that it      <p>The content model of the element is so defined that it
1008      must contain a <code><var>$0</var></code> child element.      must contain a <code><var>$0</var></code> child element.
1009      Without such an element, the document is non-conforming.</p>      The document is non-conforming.</p>
1010    
1011      <p>For example:      <dl class="switch">
1012        <ul>      <dt>HTML <code>head</code> element</dt>
1013        <li>The <code>head</code> element must contain exactly one        <dd>There must be a <code>title</code> child element.</dd>
1014        <code>title</code> child element.</li>      <dt>HTML <code>html</code> element</dt>
1015        <li><a href="#child-element-missing:td%7Cth">The <code>tr</code>        <dd>There must be a <code>head</code> child element followed
1016        element must contain one or more <code>td</code> or <code>th</code>        by a <code>body</code> element.</dd>
1017        child element.</a></li>      <dt>HTML <code>tr</code> element</dt>
1018        </ul>        <dd><a href="#child-element-missing:td%7Cth">There must be
1019      </p>        one or more <code>td</code> or <code>th</code> child element.</a></dd>
1020        </dl>
1021    </div>    </div>
1022    
1023  <div class="section content-model-error" id="child-element-missing:td|th"><h3>There must be a <code>td</code>  <div class="section" id="child-element-missing:td|th"><h3>There must be a <code>td</code>
1024    or <code>th</code> element as a child of this element.</h3>    or <code>th</code> element as a child of this element.</h3>
1025      <p>The <code>tr</code> element must contain at least one      <p>The <code>tr</code> element must contain at least one
1026      <code>td</code> or <code>th</code> child element.  Without      <code>td</code> or <code>th</code> child element.  The document
1027      such an element, the document is non-conforming.</p>      is non-conforming.</p>
1028    </div>    </div>
1029    
1030  <div class="section content-model-error" id="element-not-allowed"><h3>This element is not allowed in this  <div class="section" id="child-element-missing:atom"><h3>There must be an element
1031      <code><var>{text}</var></code> in the Atom namespace as a child of this
1032      element.</h3></div>
1033    
1034    <div class="section" id="child-element-missing:atom:link:alternate"><h3>There must be an Atom <code>link</code> element
1035      whose <code>rel</code> attribute is set to <code>alternate</code> as a
1036      child of this element.</h3></div>
1037    
1038    <div class="section" id="child-element-missing:atom:link:self"><h3>There should be an Atom <code>link</code> element
1039      whose <code>rel</code> attribute is set to <code>self</code> as a
1040      child of this element.</h3></div>
1041    
1042    <div class="section" id="element-missing:hn"><h3>There must be at least one
1043      <code>h<var>n</var></code> element descendant.</h3></div>
1044    
1045    <div class="section" id="element-not-allowed"><h3>This element is not allowed in this
1046    context.</h3>    context.</h3>
1047      <p>An element occurs where it is not allowed.  The document      <p>An element appears where it is not allowed.  The document
1048      is non-conforming.</p>      is non-conforming.</p>
1049    
1050      <p>Possible causes:      <p>Possible causes:
1051        <dl>        <dl class="switch">
1052        <dt>If the erred element is an inline-level element (such        <dt>If the element with the error is an inline-level element,
1053        as <code>a</code> or <code>span</code>)</dt>        such as <code>a</code>, <code>progress</code>, or <code>img</code></dt>
1054            <dd><p>An inline-level element cannot be a child            <dd><p>An inline-level element cannot be a child
1055            of certain sectioning elements such as <code>body</code>,            of certain sectioning elements such as <code>body</code>,
1056            <code>section</code>, and <code>blockquote</code>.</p>            <code>section</code>, and <code>blockquote</code>.</p>
1057    
1058            <p>Any inline-level content must be put            <p>Any inline-level content must be put
1059            in e.g. paragraph element such as <code>p</code>.</p></dd>            in e.g. paragraph element such as <code>p</code>.</p></dd>
1060        <dt>If the erred element is a block-level element (such as        <dt>If it is a block-level elements, such as <code>aside</code>,
1061        <code>div</code> or <code>h<var>n</var></code>)</dt>        <code>div</code>, <code>h<var>n</var></code>,
1062            <dd><p>Though some elements such as <code>div</code>,        <code>p</code>, or <code>section</code></dt>
1063            <code>li</code>, and <code>td</code> allow            <dd><dl class="switch">
1064            <em>either one</em> of block-level or inline-level content                <dt>If the parent element is <code>div</code>,
1065            is allowed.  If there is a block-level content,                <code>li</code>, <code>td</code>, or <code>th</code></dt>
1066            any inline-level content must be put                <!-- @@ TODO: more... -->
1067            in e.g. paragraph element such as <code>p</code>.</p></dd>                    <!-- @@ TODO: <p><ul><li><p> -->
1068        <dt>If the erred element is the root <code>html</code> element</dt>                    <dd><p>The parent element allows <em>either</em>
1069            <dd><p>In an XHTML document, the root <code>html</code>                    block-level or inline-level content.  If there is a
1070            element must have an <code>xmlns</code> attribute                    block-level content, any inline-level content must be
1071            whose value is set to                    put in e.g. paragraph element such as <code>p</code>.</p>
1072            <code>http://www.w3.org/1999/xhtml</code>.</p></dd>                    <p>For example, an HTML document fragment
1073                      <code class="html bad example">&lt;div&gt;&lt;p&gt;Hello!&lt;/p&gt; World!&lt;/div&gt;</code>
1074                      is non-conforming, since a word <q>World!</q> does not belong
1075                      to any paragraph.  (If not part of any paragraph, what is
1076                      it!?)  A conforming example would be:
1077                        <pre class="html example">
1078    <code>&lt;div&gt;&lt;p&gt;Hello!&lt;/p&gt; &lt;p&gt;World!&lt;/p&gt;&lt;/div&gt;</code></pre>
1079                      </p></dd>
1080                  <dt>If the parent element does <em>not</em> allow
1081                  block-level elements as content</dt>
1082                      <dd>The element is not allowed to be inserted here.
1083                      For example, a <code>div</code> element cannot be
1084                      a child of an <code>h1</code> element.</dd>
1085              </dl></dd>
1086          <dt>If the element with the error is a <code>noscript</code> element</dt>
1087              <dd>The <code>noscript</code> element is allowed only in the context
1088              where a block-level or inline-level content is expected
1089              and in the <code>head</code> element.
1090              It cannot be used in e.g. <code>ul</code>, <code>table</code>,
1091              or <code>select</code>.</dd>
1092          <dt>If the element with the error is <code>blink</code>,
1093          <code>center</code>, or <code>marquee</code> element</dt>
1094              <dd>These elements are not part of the HTML standard.
1095              Use CSS for styling control.</dd>
1096    
1097          <dt><code>button</code>, <code>datalist</code>,
1098          <code>fieldset</code>, <code>form</code>,
1099          <code>input</code>, <code>label</code>,
1100          <code>optgroup</code>, <code>option</code>, <code>output</code>,
1101          <code>rb</code>, <code>rp</code>, <code>rt</code>, <code>ruby</code>,
1102          <code>textarea</code>, or <code>textarea</code> element</dt>
1103          <!-- rbc, rtc ? -->
1104              <dd>These elements are intentionally not supported by the conformance
1105              checker <em>yet</em>.</dd>
1106        </dl>        </dl>
1107      </p>      </p>
1108    </div>    </div>
1109    
1110    <div class="section" id="element-not-allowed:area"><h3>An <code>area</code> element cannot be used
1111      outside of a <code>map</code> element.</h3></div>
1112    
1113    <div class="section" id="element-not-allowed:base"><h3>There is another <code>base</code>
1114      element.</h3></div>
1115    
1116    <div class="section" id="element-not-allowed:datatemplate"><h3>In a <code>datatemplate</code> element, only
1117      <code>rule</code> elements are allowed.</h3></div>
1118    
1119    <div class="section" id="element-not-allowed:details-legend"><h3>In a <code>details</code> element, only at the
1120      beginning of the element a <code>lengend</code> element
1121      may be used.</h3></div>
1122    
1123    <div class="section" id="element-not-allowed:empty"><h3>Elements are not allowed in an empty
1124      element.</h3></div>
1125    
1126    <div class="section" id="element-not-allowed:figure-legend"><h3>In a <code>figure</code> element, only at the
1127      beginning or only at the end of the element a <code>lengend</code> element
1128      may be used.</h3></div>
1129    
1130    <div class="section" id="element-not-allowed:flow"><h3>This element is not allowed where flow
1131      content is expected.</h3></div>
1132    
1133    <div class="section" id="element-not-allowed:flow-style"><h3>A <code>style</code> element without
1134      <code>scoped</code> attribute is not allowed in this context.</h3></div>
1135    
1136    <div class="section" id="element-not-allowed:head-noscript"><h3>This element is not allowed in a
1137      <code>noscript</code> element in the <code>head</code> element.</h3></div>
1138    
1139    <div class="section" id="element-not-allowed:head-style"><h3>A <code>style</code> element with
1140      <code>scoped</code> attribute is not allowed in the <code>head</code>
1141      element.</h3></div>
1142    
1143    <div class="section" id="element-not-allowed:head-title"><h3>There is another <code>title</code>
1144      element.</h3></div>
1145    
1146    <div class="section" id="element-not-allowed:minus"><h3>This element is not allowed in this
1147      context.</h3></div>
1148    
1149    <div class="section" id="element-not-allowed:meta-charset"><h3>The character encoding declaration is not the
1150      first child element in the <code>head</code> element.</h3>
1151        <p>The character encoding declaration
1152        (<code class="html example">&lt;meta charset="<var>...</var>"&gt;</code> or
1153        <code class="html example">&lt;meta http-equiv=Content-Type content="text/html; charset=<var>...</var>"&gt;</code>
1154        must be the first child element in the <code>head</code> element.</p>
1155    
1156        <p>The character encoding declaration have to occur near the beginning
1157        of the document to ensure that Web browsers can be determine the
1158        character encoding of the document.</p>
1159    
1160        <p>The <code>title</code> element and other metadata elements must
1161        appear after any character encoding declaration is processed.</p>
1162      </div>
1163    
1164    <div class="section" id="element-not-allowed:metadata"><h3>This element is not allowed where metadata
1165      content is expected.</h3></div>
1166    
1167    <div class="section" id="element-not-allowed:phrasing"><h3>This element is not allowed where phrasing
1168      content is expected.</h3></div>
1169    
1170    <div class="section" id="element-not-allowed:root"><h3>This element is not allowed as the root
1171      element of a document.</h3>
1172        <p>An element that is not allowed as the root element
1173        is used as the root element of the document.  The document is
1174        non-conforming, as far as the conformance checker can tell.</p>
1175    
1176        <dl class="switch">
1177        <dt><code>html</code> element in an XHTML document</dt>
1178            <dd><p>In <abbr>XHTML</abbr> document, the root <code>html</code>
1179            element must have an <code>xmlns</code> attribute as:
1180              <pre class="xml example">
1181    <code>&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;</code></pre></p></dd>
1182        <dt><code>rss</code> element</dt>
1183            <dd><p>The document is written in some version of RSS.</p>
1184            <p>The conformance checker does not support any version
1185            of RSS.  Use Atom 1.0 for feed documents.</p></dd>
1186        <dt><code>feed</code> element</dt>
1187            <dd><p>The Atom <code>feed</code> element must be
1188            in the <code>http://www.w3.org/2005/Atom</code>
1189            namespace as:
1190              <pre class="xml example">
1191    <code>&lt;feed xmlns="http://www.w3.org/2005/Atom"&gt;</code></pre>
1192            </p>
1193            <p>The conformance checker does not support Atom 0.3.
1194            Use Atom 1.0 for feed documents.</p></dd>
1195        </dl>
1196      </div>
1197    
1198    <div class="section" id="element-not-allowed:root:xml"><h3>This element is not allowed as the root element
1199      of an XML document.</h3></div>
1200    
1201    <div class="section" id="element-not-allowed:ruby-base"><h3>This element is not allowed in the <code>ruby</code>
1202      element.</h3></div>
1203    
1204    <div class="section" id="element-not-allowed:text"><h3>This element is not allowed in this
1205      context.</h3></div>
1206    
1207    <div class="section" id="element-not-allowed:atom|content"><h3>This element is not allowed in an Atom
1208      <code>content</code> element.</h3></div>
1209    
1210    <div class="section" id="element-not-allowed:atom|PersonConstruct"><h3>This element is not allowed in Person
1211      construct.</h3></div>
1212    
1213    <div class="section" id="element-not-allowed:atom|TextConstruct"><h3>This element is not allowed in Text
1214      construct.</h3></div>
1215    
1216    <div class="section" id="element-not-defined"><h3>This element is not defined.</h3>
1217        <p>The element is not one of elements allowed
1218        in the latest version of relevant specifications.</p>
1219    
1220        <p>The element cannot be used.</p>
1221    
1222        <dl class="switch">
1223        <dt><code>event-source</code> element</dt>
1224            <dd>The element was renamed as <em><code>eventsource</code>
1225            element</em> (no hyphen).</dd>
1226        <dt><code>m</code> element</dt>
1227            <dd>The element was renamed as <em><code>mark</code>
1228            element</em>.</dd>
1229        </dl>
1230      </div>
1231    
1232    <div class="section" id="no-significant-content"><h3>No significant content is contained
1233      in this element.</h3></div>
1234    
1235    <div class="section" id="no-significant-content-before"><h3>There is no significant content
1236      before this element.</h3></div>
1237    
1238    <div class="section" id="no-significant-content-at-the-end"><h3>No significant content is contained
1239      at the end of this element.</h3></div>
1240    
1241    <div class="section" id="ps-element-missing"><h3>There is no <code><var>{text}</var></code>
1242      element before this element.</h3>
1243        <p>There must be an element before another element, but there
1244        is not.  The document is non-conforming.</p>
1245    
1246        <p>For example, there must be a <code>dt</code> element
1247        before any <code>dd</code> element.</p>
1248      </div>
1249    
1250    <div class="section" id="rp:syntax-error"><h3>The content of a <code>rp</code> element must
1251      be a parenthesis.</h3></div>
1252    
1253    </section>
1254    
1255    <section id="attribute-errors">
1256    <h2>Attribute Errors</h2>
1257    
1258    <div class="section" id="attribute-missing"><h3>Required attribute <code><var>{text}</var></code>
1259      is not specified.</h3>
1260        <p>A required attribute is not specified.  The document
1261        is non-conforming.</p>
1262    
1263        <p>Some attribute is defined as <i>required</i>.
1264        Without required attributes specified, user agents
1265        cannot provide full functionality of the element to the user.</p>
1266    
1267        <dl class="switch">
1268        <dt>HTML <code>img</code> element</dt>
1269            <dd>The <code>src</code> attribute must be specified.
1270            Additionally, the <code>alt</code> attribute must be specified
1271            in many cases.</dd>
1272        <dt>HTML <code>link</code> element</dt>
1273            <dd>The <code>rel</code> attribute must be specified.
1274            Note that the <code>rev</code> attribute is obsolete.</dd>
1275        </dl>
1276      </div>
1277    
1278    <div class="section" id="attribute-missing:data|type"><h3>For an <code>object</code> at least one of
1279      <code>data</code> and <code>type</code> attributes must be
1280      specified.</h3></div>
1281    
1282    <div class="section" id="attribute-missing:href|target"><h3>For a <code>base</code> element, at least one of
1283      <code>href</code> and <code>target</code> attributes must be
1284      specified.</h3></div>
1285    
1286    <div class="section" id="attribute-missing:name|http-equiv"><h3>For a <code>meta</code> element with the
1287      <code>content</code> attribute specified, exactly one of
1288      <code>name</code> and <code>http-equiv</code> attributes must be
1289      specified.</h3></div>
1290    
1291    <div class="section" id="attribute-missing:name|http-equiv|charset"><h3>For a <code>meta</code> element, exactly one of
1292      <code>name</code>, <code>http-equiv</code>, and <code>charset</code>
1293      attributes must be specified.</h3></div>
1294    
1295    <div class="section" id="attribute-not-allowed"><h3>Attribute
1296      <code><var>{local-name}</var></code> is not allowed for
1297      <code><var>{element-local-name}</var></code> element.</h3>
1298        <p>An attribute is specified where it is not allowed.
1299        The document is non-conforming.</p>
1300    
1301        <dl>
1302        <dt>HTML <code>meta</code> element</dt>
1303            <dd>For HTML <code>meta</code> element, <em>only one</em> of
1304            <code>name</code>, <code>http-equiv</code>, or <code>charset</code>
1305            attribute is allowed.</dd>
1306        </dl>
1307      </div>
1308    
1309    <div class="section" id="attribute-not-allowed:ismap"><h3>The <code>ismap</code> attribute may only be
1310      used for the image contained in an <code>a</code> element.</h3></div>
1311    
1312    <div class="section" id="attribute-not-defined"><h3>This attribute is not defined.</h3>
1313        <p>The attribute is not one of attributes allowed for the element
1314        in the latest version of relevant specifications.</p>
1315    
1316        <p>The attribute cannot be used.</p>
1317    
1318        <dl class="switch">
1319        <dt><code>align</code> attribute (various HTML elements)</dt>
1320        <dt><code>border</code> attribute (various HTML elements)</dt>
1321          <dd>These attributes are no longer part of HTML.  You can use CSS
1322          properties to control the presentation of the element.</dd>
1323        <dt><code>autosubmit</code> attribute (<code>menu</code> element)</dt>
1324          <dd>The attribute was part of HTML5 draft but then dropped.
1325          Similar functionality can be implemented by scripts.</dd>
1326        <dt><code>language</code> attribute (<code>script</code> element)</dt>
1327          <dd>The attribute is no longer the standard way to specify the
1328          scripting language.  If you are using JavaScript, then no explicit
1329          specification of the scripting language is necessary, so you can
1330          write the element like:
1331            <p><code class="html example code">&lt;script&gt;<br><!--
1332            --> /* JavaScript code */<br><!--
1333            -->&lt;/script&gt;</code></p>
1334          If you are using different scripting language from JavaScript, or
1335          you want to declare the scripting language explicitly, you should
1336          use the <code>type</code> attribute, as follows:
1337            <dl class="switch">
1338            <dt>JavaScript</dt>
1339              <dd>Use
1340              <code class="html example">&lt;script type="text/javascript"&gt;</code>.</dd>
1341            <dt>VBScript</dt>
1342              <dd>Use
1343              <code class="html example">&lt;script type="text/vbscript"&gt;</code>.</dd>
1344            </dl>
1345          </dd>
1346        </dl>
1347      </div>
1348    
1349    <div class="section" id="in-HTML:xml:lang"><h3>The <code>xml:lang</code> attribute in HTML
1350      document is ignored.</h3>
1351        <p>The <code>xml:lang</code> attribute does not have an effect in
1352        HTML document.</p>
1353    
1354        <p>The <code>xml:lang</code> attribute is only applicable to XML
1355        documents.  In HTML document, it is only allowed to ease migration
1356        from XML.</p>
1357    
1358        <p>To specify natural language information in HTML document,
1359        use <code>lang</code> attribute instead.</p>
1360    
1361        <p>XHTML 1.0 Appendix C was encouraged to specify both
1362        <code>lang</code> and <code>xml:lang</code> attributes with
1363        the same value.  Such a duplication has <em>no effect</em> in practice.
1364        Use only one of <code>lang</code> (in HTML) or <code>xml:lang</code> (in
1365        XML).</p>
1366    
1367        <!-- @@ ISSUE: xml:lang in non-HTML element in DOM5 HTML created
1368             from an HTML document? -->
1369      </div>
1370    
1371    <div class="section" id="in-XML:charset"><h3>The <code>charset</code> attribute is not
1372      allowed in XML document.</h3>
1373        <p>The <code>charset</code> attribute of a
1374        <code>meta</code> element is not allowed in XML document.
1375        The document is non-conforming.</p>
1376    
1377        <p>To specify the character encoding used for serialization,
1378        if necessary, use XML declaration instead:
1379          <pre class="xml example">
1380    <code>&lt;?xml version="1.0" encoding="<var>encoding-name</var>"?&gt;</code></pre>
1381        </p>
1382      </div>
1383    
1384    <div class="section" id="in-XML:noscript"><h3>A <code>noscript</code> element cannot be
1385      used in XML document.</h3></div>
1386    
1387    <div class="section" id="in-XML:xml:lang"><h3>The <code>xml:lang</code> attribute in no namespace
1388      is only allowed in HTML document.</h3></div>
1389    
1390    <div class="section" id="in-XML:xmlns"><h3>The <code>xmlns</code> attribute
1391      in the <code>null</code> namespace is not allowed in
1392      XHTML document.  The document is non-conforming.</h3>
1393        <p>The <code>xmlns</code> attribute in the <code>null</code>
1394        namespace is not allowed in XHTML document.</p>
1395    
1396        <p>This error should not occur in conformance-checking of
1397        static documents.</p>
1398      </div>
1399    
1400    <div class="section" id="xml:lang-not-allowed"><h3>The <code>xml:lang</code> attribute is only allowed
1401      when the <code>lang</code> attribute is specified.</h3></div>
1402    
1403  </section>  </section>
1404    
1405  <section id="attribute-value-errors">  <section id="attribute-value-errors">
1406  <h2>Attribute Value Errors</h2>  <h2>Attribute Value Errors</h2>
1407    
1408  <div class="section attribute-error" id="enumerated:invalid"><h3>This attribute only allow a limited set of  <div class="section" id="boolean:invalid"><h3>Attribute value <code><var>{@}</var></code>
1409    values and the specified value is not one of them.</h3></div>    is not allowed.  It must be an empty string or a string
1410      <code><var>{local-name}</var></code>.</h3></div>
1411    
1412    <div class="section" id="char:syntax-error"><h3>The attribute value must be exactly one
1413      character.</h3></div>
1414    
1415    <div class="section" id="charref-in-charset"><h3>A character reference cannot be used to
1416      represent a character encoding name.</h3></div>
1417    
1418    <div class="section" id="charset:not-ascii-compat"><h3>Characeter encoding <code><var>{value}</var></code>
1419      is not ASCII compatible.</h3></div>
1420    
1421    <div class="section" id="charset:not-preferred"><h3>Character encoding name
1422      <code><var>{value}</var></code> is not the preferred name of that
1423      character encoding.</h3></div>
1424    
1425    <div class="section" id="charset:not-registered"><h3>Character encoding name
1426      <code><var>{value}</var></code> is not a registered name.</h3>
1427        <p>The specified character encoding name is not registered to
1428        <abbr>IANA</abbr>.  Use of registered character encoding name
1429        is a good practice to facilitate interoperability.</p>
1430    
1431        <dl class="switch">
1432        <dt><code>EUC-TW</code></dt>
1433          <dd><code>EUC-TW</code> is not registered.  Unfortunately, there
1434          is no registered name for that character encoding.  Use
1435          Big5 encoding with character encoding name <code>Big5</code>
1436          if it is enough to represent the document.</dd>
1437        <dt><code>ISO-2022-JP-1</code></dt>
1438          <dd><code>ISO-2022-JP-1</code> is not registered, nevertheless
1439          this character encoding name is documented in
1440          <a href="urn:ietf:rfc:2237"><abbr>RFC</abbr> 2237</a>.  Use
1441          <code>ISO-2022-JP-2</code> instead, since that character encoding
1442          is a superset of ISO-2022-JP-1.</dd>
1443        <dt><code>ISO-2022-JP-3</code>, <code>ISO-2022-JP-3-plane1</code></dt>
1444          <dd>These names are not registered and obsoleted in favor of
1445          <code>ISO-2022-JP-2004</code> and
1446          <code>ISO-2022-JP-2004-plane1</code>.</dd>
1447        <dt><code>ISO-2022-JP-2003</code>,
1448        <code>ISO-2022-JP-2003-plane1</code></dt>
1449          <dd>These names are not registered and corrected to
1450          <code>ISO-2022-JP-2004</code> and
1451          <code>ISO-2022-JP-2004-plane1</code>.</dd>
1452        <dt><code>ISO-2022-JP-2004</code>,
1453        <code>ISO-2022-JP-2004-plane1</code></dt>
1454          <dd>These names are not registered.  Unfortunately, there is
1455          no registered name for these character encodings.</dd>
1456        <dt><code>UTF-8N</code></dt>
1457          <dd><code>UTF-8N</code> is not registered.  Character encoding
1458          name <code>UTF-8</code> represents UTF-8 encoding with or
1459          without <abbr>BOM</abbr>.</dd>
1460        </dl>
1461    
1462        <p><strong>WARNING</strong>: This error might be raised for
1463        a registered character encoding name, since the character encoding
1464        name database of the conformance checker is not complete yet.</p>
1465      </div>
1466    
1467    <div class="section" id="charset:private"><h3>Character encoding name
1468      <code><var>{value}</var></code> is a private name.</h3>
1469        <p>The specified character encoding name is a private name and
1470        not registered to <abbr>IANA</abbr>.  Use of registered character
1471        encoding name is a good practice to facilitate interoperability.</p>
1472    
1473        <dl class="switch">
1474        <dt><code>x-euc-jp</code></dt>
1475          <dd>Use <code>EUC-JP</code> for the Japanese <abbr>EUC</abbr>
1476          character encoding.</dd>
1477        <dt><code>x-sjis</code></dt>
1478          <dd>Use <code>Shift_JIS</code> for standard Shift encoding scheme of
1479          <abbr>JIS</abbr> coded character set, or <code>Windows-31J</code>
1480          for Microsoft standard character set as implemented by
1481          Microsoft Windows.</dd>
1482        </dl>
1483      </div>
1484    
1485    <div class="section" id="charset:syntax-error"><h3>The specified value <code><var>{value}</var></code>
1486      is syntactically not a character encoding name.</h3>
1487        <p>The attribute value must be a character encoding name.  However,
1488        the specified value is not a character encoding name syntactically.
1489        The document is non‐conforming.</p>
1490        <p>Character encoding name is a string of <abbr>ASCII</abbr>
1491        printable characters, up to 40 characters.</p>
1492      </div>
1493    
1494    <div class="section" id="color:syntax-error"><h3>The specified value is not a color
1495      name or hexadecimal color number.</h3></div>
1496    
1497    <div class="section" id="coords:number-not-3"><h3>The <code>coords</code> attribute have to
1498      contain three (3) numbers (specified:
1499      <code><var>{text}</var></code>).</h3></div>
1500    
1501    <div class="section" id="coords:number-not-4"><h3>The <code>coords</code> attribute have to
1502      contain four (4) numbers (specified:
1503      <code><var>{text}</var></code>).</h3></div>
1504    
1505    <div class="section" id="coords:number-lt-6"><h3>The <code>coords</code> attribute have to
1506      contain more than or equal to six (6) numbers (specified:
1507      <code><var>{text}</var></code>).</h3></div>
1508    
1509    <div class="section" id="coords:number-not-even"><h3>The <code>coords</code> attribute have to
1510      contain even number of numbers (specified:
1511      <code><var>{text}</var></code>).</h3></div>
1512    
1513    <div class="section" id="coords:out-of-range"><h3>The specified value <code><var>{value}</var></code>
1514      is out of range.</h3></div>
1515    
1516    <div class="section" id="coords:syntax-error"><h3>The specified value is not valid.</h3></div>
1517    
1518    <div class="section" id="datetime:bad-year"><h3>Year number is out of range.</h3></div>
1519    
1520    <div class="section" id="datetime:bad-month"><h3>Month number is out of range.</h3></div>
1521    
1522    <div class="section" id="datetime:bad-day"><h3>Day number is out of range.</h3></div>
1523    
1524    <div class="section" id="datetime:bad-hour"><h3>Hour number is out of range.</h3></div>
1525    
1526    <div class="section" id="datetime:bad-minute"><h3>Minute number is out of range.</h3></div>
1527    
1528    <div class="section" id="datetime:bad-second"><h3>Second number is out of range.</h3></div>
1529    
1530    <div class="section" id="datetime:bad-timezone-hour"><h3>Hour number of the timezone component is out of
1531      range.</h3></div>
1532    
1533    <div class="section" id="datetime:bad-timezone-minute"><h3>Minute number of the timezone component is out of
1534      range.</h3></div>
1535    
1536    <div class="section" id="datetime:syntax-error"><h3>The attribute value is not a datetime.</h3></div>
1537    
1538    <div class="section" id="dateortime:syntax-error"><h3>The value is not a date or time.</h3></div>
1539    
1540    <div class="section" id="enumerated:invalid"><h3>This attribute only allow a limited set of
1541      values and the specified value <code><var>{@}</var></code> is not one
1542      of them.</h3>
1543        <p>For this attribute only several values are allowed and the
1544        value of the attribute is not one of them.  The document
1545        is non-conforming.</p>
1546    
1547        <dl>
1548        <dt>HTML <code>meta</code> element, <code>http-equiv</code> attribute</dt>
1549            <dd><p>Only values <code>Default-Style</code> and <code>Refresh</code>
1550            are allowed.</p>
1551            <p>Value <code>Content-Type</code> is obsolete; for charset
1552            declaration, the <code>charset</code> attribute can be used as:
1553            <pre class="html example">
1554    <code>&lt;meta charset="<var>charset-name</var>"&gt;</code></pre>
1555            ... where <var>charset-name</var> is a name of the character encoding
1556            of the document, such as <code>utf-8</code>.</p>
1557            <p>Values <code>Content-Style-Type</code> and
1558            <code>Content-Script-Type</code> are currently not allowed.</p>
1559            <p>Value <code>Keywords</code> is not allowed.  Use
1560            <code>name</code> attribute instead of <code>http-equiv</code>
1561            attribute.</p>
1562            <p>Values <code>Expires</code>, <code>Pragma</code>,
1563            and <code>Cache-Control</code> are not allowed;
1564            use <em>real</em> HTTP header fields for cache control.</p></dd>
1565        </dl>
1566      </div>
1567    
1568    <div class="section" id="enumerated:invalid:http-equiv:content-type"><h3>Character encoding declaration syntax
1569      <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"&gt;</code>
1570      is obsolete.</h3>
1571        <p>Old long character encoding declaration syntax
1572        <code class="html bad example">&lt;meta http-equiv="Content-Type" content="text/html; charset=<var>charset-name</var>"&gt;</code>
1573        is in use.  The document is non‐conforming.</p>
1574    
1575        <p>The new character encoding declaration syntax is:
1576          <pre class="html example">
1577    <code>&lt;meta charset="<var>charset-name</var>"&gt;</code></pre>
1578        </p>
1579      </div>
1580    
1581    <div class="section" id="enumerated:non-conforming"><h3>Attribute value <code><var>{@}</var></code>
1582      is not allowed.</h3></div>
1583    
1584    <div class="section" id="duplicate-http-equiv"><h3>There is another pragma
1585      <code><var>{value}</var></code>.</h3></div>
1586    
1587    <div class="section" id="duplicate-ID"><h3>This identifier has already been
1588      assigned to another element.</h3></div>
1589    
1590    <div class="section" id="duplicate-token"><h3>The token <code><var>{value}</var></code>
1591      appears in the attribute value twice.</h3></div>
1592    
1593    <div class="section" id="empty-attribute-value"><h3>The attribute value is empty.</h3></div>
1594    
1595    <div class="section" id="empty-style-sheet-title"><h3>The value of the <code>title</code> attribute
1596      is empty.</h3>
1597        <p>The <code>title</code> attribute value of the <code>link</code>
1598        element that defines an alternate style sheet is an empty value.</p>
1599    
1600        <p>A <code>link</code> element whose <code>rel</code> attribute
1601        is <code>alternate stylesheet</code> defines an alternate style sheet.
1602        An alternate style sheet must be associated with a name using the
1603        <code>title</code> attribute.  The name cannot be empty.</p>
1604      </div>
1605    
1606    <div class="section" id="float:out-of-range"><h3>The specified value is out of range.</h3></div>
1607    
1608    <div class="section" id="float:syntax-error"><h3>The attribute value is not a real
1609      number.</h3></div>
1610    
1611    <div class="section" id="fragment-points-itself"><h3>A fragment identifier references the element
1612      itself.</h3></div>
1613    
1614    <div class="section" id="fragment-points-nothing"><h3>A fragment identifier references no
1615      node.</h3></div>
1616    
1617    <div class="section" id="hashref:syntax-error"><h3>A hash−name reference must start with a
1618      <code>#</code> character.</h3></div>
1619    
1620    <div class="section" id="id-ne-name"><h3>The <code>id</code> attribute value is
1621      different from the <code>name</code> attribute value.</h3></div>
1622    
1623    <div class="section" id="integer:syntax-error"><h3>The attribute value is not an integer.</h3></div>
1624    
1625    <div class="section" id="link-type:bad-context"><h3>The link type <code><var>{value}</var></code>
1626      cannot be specified for this element.</h3>
1627        <p>The specified link type cannot be used for the element.
1628        The document is non-conforming.</p>
1629    
1630        <p>Link types are associated with limited set of elements.
1631        They cannot be used with other elements.</p>
1632    
1633        <p>For example, link type <code>bookmark</code>
1634        can be used with <code>a</code> or <code>area</code> element,
1635        while it cannot be used with <code>link</code> element.</p>
1636      </div>
1637    
1638    <div class="section" id="invalid-attribute-value"><h3>Attribute value <code><var>{@}</var></code>
1639      is not an allowed value.</h3></div>
1640    
1641    <div class="section" id="length:syntax-error"><h3>The attribute value is not a length
1642      value.</h3></div>
1643    
1644    <div class="section" id="link-type:non-conforming"><h3>The link type <code><var>{value}</var></code>
1645      is non-conforming.</h3>
1646        <p>The specified link type is non-conforming, and therefore
1647        the document is non-conforming.</p>
1648    
1649        <dl class="switch">
1650        <dt>Link type <code>contents</code></dt>
1651          <dd>Use link type <code>index</code>.</dd>
1652        <dt>Link type <code>copyright</code></dt>
1653          <dd>Use link type <code>license</code>.</dd>
1654        <dt>Link type <code>home</code></dt>
1655          <dd>Use link type <code>index</code>.</dd>
1656        <dt>Link type <code>previous</code></dt>
1657          <dd>Use link type <code>prev</code>.</dd>
1658        <dt>Link type <code>start</code></dt>
1659          <dd>Use link type <code>first</code>.</dd>
1660        <dt>Link type <code>toc</code> or <code>top</code></dt>
1661          <dd>Use link type <code>index</code>.</dd>
1662        </dl>
1663      </div>
1664    
1665    <div class="section" id="meta-content-type-syntax-error"><h3>The specified value is not a valid as a long
1666      character encoding declaration.</h3></div>
1667    
1668    <div class="section" id="mismatched-charset-name"><h3>The specified character encoding name
1669      <code><var>{value}</var></code> is different from the actual document
1670      character encoding <code><var>{text}</var></code>.</h3>
1671        <p>The specified character encoding name is different from
1672        the character encoding of the document.  The document
1673        is non‐conforming.</p>
1674      </div>
1675    
1676    <div class="section" id="mismatched-charset-name-not-checked"><h3>Whether the specified character encoding name
1677      <code><var>{value}</var></code> matches to the actual character encoding
1678      name cannot be checked since the input is not a byte stream.</h3></div>
1679    
1680    <div class="section" id="mode:syntax-error"><h3>The attribute value is not a valid mode
1681      name.</h3></div>
1682    
1683    <div class="section" id="nninteger:out-of-range"><h3>The specified value is out of range.</h3></div>
1684    
1685    <div class="section" id="nninteger:syntax-error"><h3>The attribute value is not a non‐negative
1686      integer.</h3></div>
1687    
1688    <div class="section" id="no-referenced-map"><h3>The <code>usemap</code> attribute references
1689      no image map.</h3></div>
1690    
1691    <div class="section" id="no-referenced-menu"><h3>The <code>contextmenu</code> attribute references
1692      no menu.</h3></div>
1693    
1694    <div class="section" id="no-referenced-header-cell"><h3>There is no table header cell whose <code>id</code>
1695      is <code><var>{value}</var></code> in the same table.</h3></div>
1696    
1697    <div class="section" id="refresh:syntax-error"><h3>the specified value is not a valid as part
1698      of a <code>Refresh</code> pragma.</h3></div>
1699    
1700    <div class="section" id="repeat:syntax-error"><h3>The attribute value is not an integer or
1701      a string <code>template</code>.</h3></div>
1702    
1703    <div class="section" id="reserved-browsing-context-name"><h3>Browsing context name
1704      <code><var>{@}</var></code> is reserved.</h3>
1705        <p>The specified browsing context name is reserved.
1706        The document is non-conforming.</p>
1707    
1708        <p>Names of browsing contexts starting with <code>_</code>
1709        (<code>U+005F</code> <code class="charname">LOW LINE</code>)
1710        are reserved so that it must not be used.</p>
1711    
1712        <p>Old version of HTML, non-HTML markup languages, and
1713        Web browsers define or implements special reserved
1714        browsing context names <code>_blank</code>,
1715        <code>_main</code>, and <code>_replace</code>.
1716        However, they are <em>not</em> conforming attribute values.</p>
1717      </div>
1718    
1719    <div class="section" id="Reserved-Prefixes-and-Namespace-Names:Name"><h3>Namespace name <code><var>{text}</var></code>
1720      is reserved and cannot be used for an arbitrary prefix.</h3></div>
1721    
1722    <div class="section" id="Reserved-Prefixes-and-Namespace-Names:Prefix"><h3>Namespace prefix <code><var>{text}</var></code>
1723      is reserved and cannot be used for an arbitrary namespace name.</h3></div>
1724    
1725    <div class="section" id="link-type:proposed"><h3>Link type <code><var>{value}</var></code>
1726      is proposed but not accepted yet; it <em>should not</em> be
1727      used until it has been accepted.</h3>
1728        <p>The link type is in the <i>proposed</i> status; it
1729        <em>should not</em> be used until it has been
1730        accepted.</p>
1731    
1732        <p><strong>Warning</strong>: The data served to the
1733        conforming checker might be out of date; it might have already
1734        been accepted or rejected.  The document might or might not be
1735        conforming depending on the status.  See WHATWG Wiki
1736        for the latest information.</p>
1737      </div>
1738    
1739    <div class="section" id="sizes:syntax-error"><h3>The specified value <code><var>{value}</var></code>
1740      is not a valid value.</h3></div>
1741    
1742    <div class="section" id="space-in-ID"><h3>White space characters are not allowed
1743      in the <code>id</code> attribute.</h3></div>
1744    
1745    <div class="section" id="template:not-template"><h3>The node referenced by the <code>template</code>
1746      attribute is not a template.</h3></div>
1747    
1748    <div class="section" id="window-name:empty"><h3>Browsing context name must not be empty.</h3></div>
1749    
1750    <div class="section" id="window-name:reserved"><h3>Browsing context name
1751      <code><var>{value}</var></code> is reserved.</h3></div>
1752    
1753    <div class="section" id="word-not-allowed"><h3>The word <code><var>{value}</var></code> is not
1754      allowed in this attribute.</h3></div>
1755    
1756    <div class="section" id="XML-1.0-NCName:syntax-error"><h3>The specified value is not a legal XML Namespaces
1757      1.0 <code>NCName</code>.</h3></div>
1758    
1759    <div class="section" id="xml:lang-ne-lang"><h3>The value of the <code>xml:lang</code> attribute
1760      is different from the value of the <code>lang</code> attribute.</h3>
1761        <p>The value of the <code>xml:lang</code> attribute (either the
1762        <code>lang</code> attribute in the <code>xml</code> (i.e.
1763        <code>http://www.w3.org/XML/1998/namespace</code>) namespace, or
1764        the <code>xml:lang</code> attribute in no namespace) for the element has
1765        different value than that of the <code>lang</code> attribute in no
1766        namespace.</p>
1767    
1768        <p>For historical reason, there are two attributes applicable to HTML
1769        elements to specify language information of an element: <code>lang</code>
1770        and <code>xml:lang</code>.  In HTML documents, only <code>lang</code>
1771        attribute in no namespace is allowed and take effect; the
1772        <code>xml:lang</code> attribute in no namespace is ignored in HTML
1773        documents.  In XHTML documents, both <code>lang</code> and
1774        <code>xml:lang</code> attributes are allowed.</p>
1775    
1776        <p>In general, <em>only the <code>lang</code> attribute</em> need to be
1777        specified for an element.</p>
1778    
1779        <p>If both <code>lang</code> and <code>xml:lang</code> attributes are
1780        specified on the same element, their values must be the same value.</p>
1781      </div>
1782    
1783  </section>  </section>
1784    
1785  <section id="table-model-errors">  <section id="table-model-errors">
1786  <h2>Table Model Errors</h2>  <h2>Table Model Errors</h2>
1787    
1788  <div class="section table-model-error" id="table:no-cell-in-last-row"><h3>The table has no cell (<code>td</code> or  <div class="section" id="cell-overlapping"><h3>Cell slot (<var>{text}</var>) is filled by
1789      multiple cells.</h3></div>
1790    
1791    <div class="section" id="colspan-creates-column-with-no-anchored-cell"><h3>This <code>colspan</code> attribute
1792      results in creating a table column that does not contain
1793      any cell anchored to it.</h3></div>
1794    
1795    <div class="section" id="column-with-no-anchored-cell"><h3>This column has no anchored cell.</h3></div>
1796    
1797    <div class="section" id="table:no-cell-in-last-row"><h3>The table has no cell (<code>td</code> or
1798    <code>th</code>) in the last row.</h3></div>    <code>th</code>) in the last row.</h3></div>
1799    
1800    <div class="section" id="table:rowspan-extends-table"><h3>This <code>rowspan</code> attribute
1801      results in creating a table row that does not contain
1802      any cell anchored to it.</h3>
1803        <p>The <code>rowspan</code> attribute value of the cell
1804        is so specified that it extends a table in the row axis.
1805        However, the extended row does not contain any cell by itself.
1806        The document is non-conforming.</p>
1807    
1808        <p>For example, the table below is non-conforming:
1809          <pre class="html bad example">
1810    <code>&lt;table&gt;
1811    &lt;tbody&gt;
1812    &lt;tr&gt;&lt;td rowspan=2&gt;&lt;/td&gt;&lt;/tr&gt;
1813    &lt;/tbody&gt;
1814    &lt;/table&gt;</code></pre>
1815        ... since the second row contains only
1816        a cell that spans between first and second rows.</p>
1817      </div>
1818    
1819    <div class="section" id="row-with-no-anchored-cell"><h3>This row has no anchored cell.</h3></div>
1820    
1821    <div class="section" id="rowspan-creates-row-with-no-anchored-cell"><h3>This <code>rowspan</code> attribute
1822      results in creating a table row that does not contain
1823      any cell anchored to it.</h3></div>
1824    
1825    
1826  </section>  </section>
1827    
1828  <section id="imt-warnings">  <section id="imt-warnings">
1829  <h2>Internet Media Type Warnings</h2>  <h2>Internet Media Type Errors</h2>
1830    
1831    <div class="section" id="boundary:syntax-error"><h3>The specified value is not a valid value
1832      as a multipart boundary.</h3></div>
1833    
1834  <div class="section should" id="s:IMT:obsolete-subtype"><h3>An <em>obsolete</em> subtype is used.</h3></div>  <div class="section" id="e4x:syntax-error"><h3>The specified value is not a valid value
1835      for the attribute <code>e4x</code>.</h3></div>
1836    
1837  <div class="section should" id="s:IMT:private-subtype"><h3>A private (<code>x-</code> or <code>x.</code>)  <div class="section" id="IMT:attribute-syntax-error"><h3>The specified value,
1838    subtype is used.</h3></div>    <code><var>{value}</var></code>, is syntactically not a valid
1839      attribute name.</h3></div>
1840    
1841    <div class="section" id="IMT:composite"><h3>The specified media type is a composite
1842      type, which is not allowed in this context.</h3></div>
1843    
1844    <div class="section" id="IMT:limited-use-subtype"><h3>An Internet Media Type whose intended usage
1845      is limited use, <code><var>{value}</var></code> is used.</h3></div>
1846    
1847    <div class="section" id="IMT:syntax-error"><h3>The specified value is not an Internet Media
1848      Type.</h3></div>
1849    
1850    <div class="section" id="IMT:obsolete-parameter"><h3>An obsolete parameter
1851      <code><var>{value}</var></code> is used.</h3></div>
1852    
1853    <div class="section" id="IMT:obsolete-subtype"><h3>An obsolete Internet Media Type
1854      <code><var>{value}</var></code> is used.</h3>
1855        <p>The specified Internet Media Type is registered with its intended
1856        usage as <i>OBSOLETE</i>.</p>
1857        
1858        <dl class="swtich">
1859        <dt>Media type <code>text/ecmascript</code></dt>
1860          <dd>Media type <code>text/ecmascript</code> is obsoleted in
1861          favor of <code>application/ecmascript</code>.  Note that
1862          <em><code>text/javascript</code></em> would be the better alternative
1863          in many cases.</dd>
1864        <dt>Media type <code>text/javascript</code></dt>
1865          <dd>Media type <code>text/javascript</code> is obsoleted by
1866          <abbr>IETF</abbr> with backward incompatible alternate
1867          <code>application/javascript</code> for architectural
1868          purity.<!-- @@ ref? -->  Those who prefer reality to academic
1869          purity <em>may ignore</em> this warning.</dd>
1870        </dl>
1871      </div>
1872    
1873    <div class="section" id="IMT:parameter-missing"><h3>Parameter <code><var>{text}</var></code> have to
1874      be specified for the Internet Media Type
1875      <code><var>{value}</var></code>.</h3></div>
1876    
1877    <div class="section" id="IMT:parameter-not-allowed"><h3>Parameter <code><var>{value}</var></code> is not
1878      allowed for this Internet Media Type.</h3></div>
1879    
1880    <div class="section" id="IMT:private-subtype"><h3>Use of a private Internet Media Type
1881      <code><var>{value}</var></code> is not encouraged.</h3></div>
1882    
1883    <div class="section" id="IMT:private-type"><h3>Use of a private type
1884      <code><var>{value}</var></code> is not encouraged.</h3></div>
1885    
1886    <div class="section" id="IMT:subtype-syntax-error"><h3>Value <code><var>{value}</var></code> is
1887      syntactically not a valid subtype value of an Internet Media Type.</h3></div>
1888    
1889    <div class="section" id="IMT:type-syntax-error"><h3>Value <code><var>{value}</var></code> is
1890      syntactically not a valid type.</h3></div>
1891    
1892    <div class="section" id="IMT:unknown-parameter"><h3>An unknown parameter <code><var>{value}</var></code>
1893      is used.  The conformance checker cannot determine whether use of this
1894      parameter is valid or not.</h3></div>
1895    
1896    <div class="section" id="IMT:unknown-subtype"><h3>An unknown Internet Media Type
1897      <code><var>{value}</var></code> is used.  At the time of the update of
1898      the conformance checker's Internet Media Type database, the subtype is
1899      not reigstered to the IANA registry.  The subtype, however, might be
1900      registerd to the IANA registry thereafter.  Please consult the IANA
1901      registry.</h3></div>
1902    
1903    <div class="section" id="IMT:unregistered-subtype"><h3>Use of an Internet Media Type
1904      <code><var>{value}</var></code> is not encouraged since it is not
1905      part of the IANA registry.</h3></div>
1906    
1907    <div class="section" id="IMT:unregistered-type"><h3>Use of a type
1908      <code><var>{value}</var></code> is not encouraged since it is not
1909      a standardized type.</h3></div>
1910    
1911  <div class="section should" id="s:IMT:unregistered-subtype"><h3>The subtype is not registered to IANA.</h3></div>  <div class="section" id="not-IMT"><h3>A value that is not an Internet Media Type
1912      is not allowed here.</h3></div>
1913    
1914  </section>  </section>
1915    
1916  <section id="uri-errors">  <section id="uri-errors">
1917  <h2>URI (or IRI) Errors</h2>  <h2>URL Errors</h2>
1918    
1919    <div class="section" id="syntax-error:iri3987"><h3>The specified value is syntactically not an
1920      IRI.</h3></div>
1921    
1922  <div class="section must" id="m:URI::syntax-error"><h3>This string is not an IRI syntactically.</h3></div>  <div class="section" id="syntax-error:iriref3987"><h3>The specified value is syntactically not an IRI
1923      reference.</h3>
1924        <p>The specified value does not satisfy the syntactical requirements
1925        for IRI references.  The document is non-conforming.</p>
1926    
1927        <p>Possible causes:
1928          <ul>
1929          <li>The string might contain one or more white space characters.
1930          Especially, the <code> </code> (<code>U+0020</code>
1931          <code class="charname">SPACE</code>) character cannot be
1932          used in IRI references.</li>
1933          </ul>
1934        </p>
1935      </div>
1936    
1937    <div class="section" id="syntax-error:rdfuriref"><h3>The specified value is syntactically not an RDF
1938      URI reference.</h3></div>
1939    
1940    <div class="section" id="syntax-error:uri2396"><h3>The specified value is syntactically not a
1941      URI according to RFC 2396.</h3></div>
1942    
1943    <div class="section" id="syntax-error:uri3986"><h3>The specified value is syntactically not a
1944      URI.</h3></div>
1945    
1946    <div class="section" id="URL:address-format"><h3>URL host address format
1947      <code><var>{text}</var></code> is not defined.</h3></div>
1948    
1949    <div class="section" id="URL:default-port"><h3>Default port number should be omitted.</h3></div>
1950    
1951    <div class="section" id="URL:dot-segment"><h3>A dot-segment (<code>.</code> or
1952      <code>..</code>) occurs in an absolute reference.</h3>
1953        <p>Dot-segment (<code>.</code> or <code>..</code>) should
1954        not occur in an absolute reference.</p>
1955    
1956        <p>In relative references, dot-segments are used to represent
1957        the current (<code>.</code>) or the parent (<code>..</code>)
1958        hierarchy of the path.  Though they are also allowed
1959        in absolute references, it should be resolved to the
1960        canonical form before it has been published.</p>
1961      </div>
1962    
1963    <div class="section" id="URL:empty-host"><h3>The host component of the URL is empty.</h3></div>
1964    
1965    <div class="section" id="URL:empty-path"><h3>The URL does not end with
1966      a <code>/</code> character.</h3></div>
1967    
1968    <div class="section" id="URL:empty-port"><h3>The port component of the URL is empty.</h3></div>
1969    
1970    <div class="section" id="URL-fragment-not-allowed"><h3>The fragment component of the URL is not
1971      allowed.</h3></div>
1972    
1973    <div class="section" id="URL:long-host"><h3>The host component of the URL
1974      is too long.</h3></div>
1975    
1976    <div class="section" id="URL:lowercase-hexadecimal-digit"><h3>A lowercase hexadecimal digit is used
1977      in percent-encoding.</h3>
1978        <p>The hexadecimal digit in percent-encoding string in the IRI
1979        is in lowercase.  Though the IRI <em>is</em> conforming,
1980        it should be in uppercase.</p>
1981      </div>
1982    
1983    <div class="section" id="URL:non-DNS-host"><h3>The host component of the URL
1984      is not a DNS host name.</h3></div>
1985    
1986    <div class="section" id="URL:non-UTF-8-host"><h3>The host component of the URL
1987      is not encoded in UTF-8.</h3></div>
1988    
1989    <div class="section" id="URL:password"><h3>Password should not be included in a URL
1990      for the security.</h3></div>
1991    
1992    <div class="section" id="URL:percent-encoded-unreserved"><h3>An unreserved character is
1993      percent-encoded.</h3>
1994        <p>An unreserved character is percent-encoded in the IRI.
1995        Though it <em>is</em> conforming, it should be in the
1996        decoded (or bare) form.</p>
1997      </div>
1998    
1999    <div class="section" id="URL:uppercase-host"><h3>The host <code><var>{value}</var></code>
2000      should be spelt in lowercase.</h3></div>
2001    
2002    <div class="section" id="URL:uppercase-scheme-name"><h3>URL scheme name is in uppercase.</h3>
2003        <p>The scheme part of the IRI is written in uppercase letter.</p>
2004    
2005        <p>Uppercase scheme names are not required to be processed
2006        correctly.</p>
2007    <!-- @@
2008     RFC 3986 3.1.
2009     > Although schemes are case-
2010       insensitive, the canonical form is lowercase and documents that
2011       specify schemes must do so with lowercase letters.
2012    
2013     > An implementation ... should only produce lowercase scheme names for
2014       consistency.
2015    -->
2016      </div>
2017    
2018  </section>  </section>
2019    
2020  <section id="uri-errors">  <section id="mq-errors">
2021  <h2>URI (or IRI) Errors</h2>  <h2>Media Query Errors</h2>
2022    
2023    <div class="section" id="mq-syntax-error"><h3>The specified value has a syntax error as a
2024      media query.</h3></div>
2025    
2026    <div class="section" id="unknown-media-type"><h3>Media type <code><var>{value}</var></code> is
2027      not supported by the conformance checker.</h3></div>
2028    
2029    </section>
2030    
2031    <section id="selectors-errors">
2032    <h2>Selectors Errors</h2>
2033    
2034    <div class="section" id="an+b-not-closed"><h3>Argument list of the pseudo-class is
2035      not closed by a <code>)</code> character.</h3></div>
2036    
2037    <div class="section" id="ab+b-not-integer"><h3>Numbers in the argument
2038      <code><var>a</var>n+<var>b</var></code> have to be integers.</h3></div>
2039    
2040    <div class="section" id="an+b-syntax-error"><h3>Argument <code><var>a</var>n+<var>b</var></code> is
2041      syntactically incorrect.</h3></div>
2042    
2043    <div class="section" id="attr-selector-not-closed"><h3>Attribute selector is not closed by
2044      a <code>]</code> character.</h3></div>
2045    
2046    <div class="section" id="lang-selector-not-closed"><h3>Argument list of the <code>:lang</code>
2047      selector is not closed by a <code>)</code> character.</h3></div>
2048    
2049    <div class="section" id="namespace-prefix:not-declared"><h3>Namespace prefix <code><var>{value}</var></code>
2050      is not declared.</h3></div>
2051    
2052    <div class="section" id="no-attr-local-name"><h3>Attribute local name is missing.</h3></div>
2053    
2054    <div class="section" id="no-attr-match"><h3>Attribute matching operator (e.g.
2055      <code>=</code>) is missing.</h3></div>
2056    
2057    <div class="section" id="no-attr-name"><h3>Attribute name is missing.</h3></div>
2058    
2059    <div class="section" id="no-attr-namespace-separator"><h3>Attribute namespace wildcard <code>*</code>
2060      is not followed by a <code>|</code> character.</h3></div>
2061    
2062    <div class="section" id="no-attr-value"><h3>Attribute value is missing.</h3></div>
2063    
2064    <div class="section" id="no-class-name-selector"><h3>Class name is missing.</h3></div>
2065    
2066    <div class="section" id="no-combinator"><h3>Combinator is missing.</h3></div>
2067    
2068    <div class="section" id="no-contains-string"><h3>No string is specified in the argument
2069      list of the <code>:-manakai-contains</code> pseudo-class
2070      selector.</h3></div>
2071    
2072    <div class="section" id="no-lang-tag"><h3>Language tag argument is missing.</h3></div>
2073    
2074    <div class="section" id="no-local-name-selector"><h3>Local name part of the type selector (or
2075      <code>*</code> for the universal selector) is missing.</h3></div>
2076    
2077    <div class="section" id="no-pseudo-class-name"><h3>Pseudo-class name is missing.</h3></div>
2078    
2079  <div class="section should" id="s:URI::empty-path"><h3>This IRI should explicitly end with  <div class="section" id="no-pseudo-element-name"><h3>Pseudo-element name is missing.</h3></div>
2080    <code>/</code>.</h3></div>  
2081    <div class="section" id="no-sss"><h3>Sequence of simple selectors is
2082      expected.</h3></div>
2083    
2084    <div class="section" id="not-not-closed"><h3>Argument list of the <code>:not</code> selector
2085      is not closed by a <code>)</code> character.</h3></div>
2086    
2087    <div class="section" id="ss-after-pseudo-element"><h3>Simple selector is not allowed after a
2088      pseudo element.</h3></div>
2089    
2090    <div class="section" id="unknown-pseudo-class"><h3>Pseudo-class <code>:<var>{value}</var></code>
2091      is not supported by the conformance checker.</h3></div>
2092    
2093    <div class="section" id="unknown-pseudo-element"><h3>Pseudo-element <code>::<var>{value}</var></code>
2094      is not supported by the conformance checker.</h3></div>
2095    
2096    </section>
2097    
2098    <section id="css-errors">
2099    <h2>CSS Errors</h2>
2100    
2101    <div class="section" id="at-rule-not-allowed"><h3>An <code>@<var>{text}</var></code> rule is not
2102      allowed here.</h3></div>
2103    
2104    <div class="section" id="at-rule-syntax-error"><h3>The <code>@<var>{text}</var></code> rule is
2105      syntactically incorrect.</h3></div>
2106    
2107    <div class="section" id="block-not-closed"><h3>Block is not closed before the end of
2108      file.</h3></div>
2109    
2110    <div class="section" id="CSS-duplication"><h3>Component <code>&lt;<var>{text}</var>&gt;</code> is
2111      already specified.</h3></div>
2112    
2113    <div class="section" id="CSS-cursor-hand"><h3>Value <code>hand</code> is not valid as
2114      <code>&lt;'cursor'&gt;</code>.</h3></div>
2115    
2116    <div class="section" id="CSS-syntax-error"><h3>Specified value is syntactically not a correct
2117      <code>&lt;<var>{text}</var>&gt;</code>.</h3></div>
2118    
2119    <div class="section" id="no-declaration-block"><h3>No declaration block is found after a group of
2120      selectors.</h3></div>
2121    
2122    <div class="section" id="no-property-colon"><h3>A <code>:</code> character is missing after
2123      a property name.</h3></div>
2124    
2125    <div class="section" id="no-property-name"><h3>Property name is expected.</h3></div>
2126    
2127    <div class="section" id="no-property-semicolon"><h3>A <code>;</code> character is missing at the
2128      end of the property.</h3></div>
2129    
2130    <div class="section" id="priority-syntax-error"><h3>Priority part of the declaration is syntactically
2131      incorrect.</h3></div>
2132    
2133    <div class="section" id="unknown-at-rule"><h3>The <code>@<var>{value}</var></code> rule is
2134      not supported by the conformance checker.</h3></div>
2135    
2136    <div class="section" id="unknown-property"><h3>Property <code><var>{value}</var></code> is
2137      not supported by the conformance checker.</h3></div>
2138    
2139    </section>
2140    
2141    <section id="cache-manifest-errors">
2142    <h2>Cache Manifest Errors</h2>
2143    
2144    <div class="section" id="both-in-entries-and-whitelist"><h3>This URL is found both in the explicit or
2145      fallback entries and in the online whitelist.</h3></div>
2146    
2147    <div class="section" id="different-origin-from-manifest"><h3>The specified URL has different origin from
2148      the manifest.</h3></div>
2149    
2150    <div class="section" id="different-scheme-from-manifest"><h3>The scheme component of the URL is
2151      different from that of the manifest URL.  The URL is ignored.</h3></div>
2152    
2153    <div class="section" id="duplicate-oc-namespace"><h3>This oppotunistic caching namespace is already
2154      specified.</h3></div>
2155    
2156    <div class="section" id="no-fallback-entry-URL"><h3>Fallback entry URL is missing.</h3></div>
2157    
2158    <div class="section" id="not-manifest"><h3>This document is not a cache manifest.</h3>
2159        <p>The specified document is <em>not</em> a cache manifest.
2160        The document is non-conforming.</p>
2161    
2162        <p>An entity labeled as Internet media type
2163        <code>text/cache-manifest</code> must contain a cache manifest.</p>
2164    
2165        <p>A cache manifest must start with a line whose content is
2166        <code class="manifest example">CACHE MANIFEST</code>
2167        (exactly one space character between
2168        <code>CACHE</code> and <code>MANIFEST</code>).</p>
2169      </div>
2170    
2171    <div class="section" id="same-as-manifest-URL"><h3>This URL is same as the manifest URL.</h3></div>
2172    
2173    </section>
2174    
2175    <section id="webidl-errors">
2176    <h2>WebIDL Errors</h2>
2177    
2178    <div class="section" id="after-argument"><h3>An argument name is not followed by a
2179      <code>,</code> character or a <code>)</code> character.</h3></div>
2180    
2181    <div class="section" id="after-exception-name"><h3>An exception name is not followed by a
2182      <code>,</code> character or a <code>)</code> character.</h3></div>
2183    
2184    <div class="section" id="after-unsigned"><h3>キーワード <code>unsigned</code> の後の字句が
2185      <code>short</code> か <code>long</code> ではありません。</h3></div>
2186    
2187    <div class="section" id="after-xattr"><h3>An extended attribute is not followed by
2188      a <code>,</code> character or a <code>]</code> character.</h3></div>
2189    
2190    <div class="section" id="argument-after-variadic"><h3>An argument is specified after an argument
2191      with <code>Variadic</code> extended attribute is seen.</h3></div>
2192    
2193    <div class="section" id="attr-not-readonly"><h3>Extended attribute <code><var>{text}</var></code> is
2194      specified for an attribute that is not read-only.</h3></div>
2195    
2196    <div class="section" id="attr-type-not-interface"><h3>Extended attribute <code><var>{text}</var></code>
2197      is specified for an attribute whose type is not an interface.</h3></div>
2198    
2199    <div class="section" id="before-exception-member"><h3>An unknown construct is found where an exception
2200      member or a <code>}</code> character is expected.</h3></div>
2201    
2202    <div class="section" id="before-interface-member"><h3>An unknown construct is found where an interface
2203      member or a <code>}</code> character is expected.</h3></div>
2204    
2205    <div class="section" id="before-webidl-block"><h3>An identifier for the <code><var>{text}</var></code>
2206      is not followed by a <code>{</code> character.</h3></div>
2207    
2208    <div class="section" id="before-webidl-def"><h3>An unknown construct is found after an
2209      extended attribute list (where a <code>Definition</code> is
2210      expected).</h3></div>
2211    
2212    <div class="section" id="before-webidl-defs"><h3>An unknown construct is found where a
2213      <code>Definition</code> (optionally preceded by an extended attribute list)
2214      is expected.</h3></div>
2215    
2216    <div class="section" id="before-webidl-type"><h3>The type for <code><var>{text}</var></code> is
2217      not specified.</h3></div>
2218    
2219    <div class="section" id="before-webidl-type:argument"><h3>The type for an argument is not
2220      specified.</h3></div>
2221    
2222    <div class="section" id="before-webidl-type:exception-member"><h3>The type for an exception member is not
2223      specified.</h3></div>
2224    
2225    <div class="section" id="before-xattr"><h3>No extended attribute is specified after
2226      a <code>[</code> character.</h3></div>
2227    
2228    <div class="section" id="before-xattrarg"><h3>No identifier is specified in an extended
2229      attribute assignment.</h3></div>
2230    
2231    <div class="section" id="const-value-out-of-range"><h3>The specified value <code><var>{value}</var></code>
2232      is outside of the range of the type for the constant,
2233      <code><var>{text}</var></code>.</h3></div>
2234    
2235    <div class="section" id="const-type-mismatch"><h3>The type of the value,
2236      <code><var>{value}</var></code>, is different from the type of the constant,
2237      <code><var>{text}</var></code>.</h3></div>
2238    
2239    <div class="section" id="duplicate-accessor"><h3>Extended attribute <code><var>{text}</var></code>
2240      is already specified for another operation in the same interface.</h3></div>
2241    
2242    <div class="section" id="duplicate-constructor-name"><h3>Constructor name <code><var>{value}</var></code>
2243      specified by extended attribute <code><var>{text}</var></code> is already
2244      used for an interface.</h3></div>
2245    
2246    <div class="section" id="duplicate-member"><h3>Name <code><var>{text}</var></code> is
2247      already used.</h3></div>
2248    
2249    <div class="section" id="duplicate-qname"><h3>Qualified name <code><var>{text}</var></code> is
2250      already used.</h3></div>
2251    
2252    <div class="section" id="duplicate-xattr"><h3>Extended attribute <code><var>{text}</var></code>
2253      is already specified.</h3></div>
2254    
2255    <div class="section" id="exception-not-defined"><h3>Exception <code><var>{text}</var></code> is
2256      not defined in the fragment.</h3></div>
2257    
2258    <div class="section" id="interface-not-defined"><h3>Interface <code><var>{text}</var></code> is
2259      not defined in the fragment.</h3></div>
2260    
2261    <div class="section" id="no-arguments-in"><h3>No <code>in</code> keyword for an argument is
2262      found.</h3></div>
2263    
2264    <div class="section" id="no-arguments-lparen"><h3>No <code>(</code> character for an argument
2265      list is found.</h3></div>
2266    
2267    <div class="section" id="no-raises-lparen"><h3>A <code>raises</code> (or <code>getraises</code>
2268      or <code>setraises</code>) keyword is not followed by a <code>(</code>
2269      character.</h3></div>
2270    
2271    <div class="section" id="no-sequence-gt"><h3>A <code>sequence&lt;&gt;</code> type is not
2272      terminated by a <code>&gt;</code> character.</h3></div>
2273    
2274    <div class="section" id="no-sequence-lt"><h3>Keyword <code>sequence</code> is not followed
2275      by a <code>&lt;</code> character.</h3></div>
2276    
2277    <div class="section" id="no-sequence-type"><h3>No type is specified in
2278      <code>sequence&lt;&gt;</code>.</h3></div>
2279    
2280    <div class="section" id="no-webidl-identifier"><h3>No identifier is specified for the
2281      <code><var>{text}</var></code>.</h3></div>
2282    
2283    <div class="section" id="no-webidl-identifier:argument"><h3>No identifier is specified for the
2284      argument.</h3></div>
2285    
2286    <div class="section" id="no-webidl-identifier:exception-member"><h3>No identifier is specified for the
2287      exception member.</h3></div>
2288    
2289    <div class="section" id="no-webidl-identifier:operation"><h3>No identifier is specified for the
2290      operation.</h3></div>
2291    
2292    <div class="section" id="no-webidl-semicolon"><h3>No semicolon is found at the end of the
2293      definition or member.</h3></div>
2294    
2295    <div class="section" id="non-module-definition"><h3>This definition is not part of any
2296      module.</h3></div>
2297    
2298    <div class="section" id="not-boxable-type"><h3>Type <code><var>{text}</var></code> cannot be
2299      used in <code>valuetype</code>.</h3></div>
2300    
2301    <div class="section" id="premature-end-of-webidl"><h3>The WebIDL fragment ends before all the blocks
2302      are closed by <code>};</code> sequences.</h3></div>
2303    
2304    <div class="section" id="referenced-attr-not-defined"><h3>Attribute <code><var>{value}</var></code> is
2305      not defined in the interface specified for the attribute to which
2306      extended attribute <code><var>{text}</var></code> is set.</h3></div>
2307    
2308    <div class="section" id="scoped-name"><h3>A scoped name is expected here.</h3></div>
2309    
2310    <div class="section" id="scoped-name:dcolon"><h3>A <code>::</code> token is not followed by
2311      an identifier or a <code>DOMString</code> keyword.</h3></div>
2312    
2313    <div class="section" id="type-not-defined"><h3>Type <code><var>{text}</var></code> is not
2314      defined.</h3></div>
2315    
2316    <div class="section" id="typedef-ignored"><h3><code>typedef</code> of name <code>DOMString</code>
2317      is ignored.</h3></div>
2318    
2319    <div class="section" id="unknown-xattr"><h3>An unknown extended attribute
2320      <code><var>{text}</var></code> is used.</h3></div>
2321    
2322    <div class="section" id="valuetype-DOMString"><h3>The <code>valuetype</code> definition does
2323      not define <code>DOMString</code> as
2324      <code>sequence&lt;unsigned short&gt;</code>.</h3></div>
2325    
2326    <div class="section" id="valuetype-ignored"><h3><code>valuetype</code> of name
2327      <code>DOMString</code> is ignored.</h3></div>
2328    
2329    <div class="section" id="wrong-signature-accessor"><h3>The operation cannot be used as accessor operation
2330      of <code><var>{text}</var></code>, since its signature different from
2331      the expected one.</h3></div>
2332    
2333    <div class="section" id="xattr-arglist-not-allowed"><h3>Use of an argument list for extended attribute
2334      <code><var>{text}</var></code> is not allowed.</h3></div>
2335    
2336    <div class="section" id="xattr-for-wrong-type"><h3>Extended attribute <code><var>{text}</var></code>
2337      is not applicable for an attribute whose type is not
2338      <code>DOMString</code>.</h3></div>
2339    
2340    <div class="section" id="xattr-id-missing"><h3>The identifier for extended attribute
2341      <code><var>{text}</var></code> is not specified.</h3></div>
2342    
2343    <div class="section" id="xattr-id-not-allowed"><h3>Use of an identifier for extended attribute
2344      <code><var>{text}</var></code> is not allowed.</h3></div>
2345    
2346    <div class="section" id="xattr-id-value-not-allowed"><h3>The identifier <code><var>{value}</var></code> is
2347      not an allowed value for extended attribute
2348      <code><var>{text}</var></code>.</h3></div>
2349    
2350    <div class="section" id="xattr-not-applicable"><h3>Extended attribute <code><var>{text}</var></code>
2351      is not applicable to this kind of object.</h3></div>
2352    
2353    </section>
2354    
2355    <section id="information">
2356    <h2>Stability Information</h2>
2357    
2358    <div class="section" id="deprecated:attr"><h3>This attribute is deprecated.</h3></div>
2359    
2360    <div class="section" id="deprecated:element"><h3>This element is deprecated.</h3></div>
2361    
2362    <div class="section" id="status:cr:element"><h3>This element is in the
2363      <strong>call for implementation</strong> stage.</h3>
2364        <p>The element is in the call for implementation stage.</p>
2365        
2366        <p>Usually, using the element is safe.  However, it is a new feature
2367        so that it might not be implemented correctly.  If it is found that
2368        the feature is hard or impossible to implement, the feature
2369        might be revised, or in some case it might be dropped.</p>
2370    
2371        <p>Elements defined by Atom 1.0 (IETF Proposed Standard), and XBL 2.0
2372        (W3C Candidate Recommendation) belong to this class.</p>
2373      </div>
2374    
2375    <div class="section" id="status:lc:element"><h3>This element is in the <strong>last
2376      call for comments</strong> stage.</h3>
2377        <p>The element is in the last call for comments stage.</p>
2378        
2379        <p>The element is relatively mature, though the standardization
2380        is not done yet.  It may be used for experiments.  Since it is a new
2381        feature, it might not be implemented correctly or at all.  If it is
2382        found that the feature is hard or impossible to implement, the feature
2383        might be revised or might be dropped.</p>
2384    
2385        <p>Elements defined by Web Forms 2.0 as well as some elements
2386        defined by HTML5 belong to this class.</p>
2387      </div>
2388    
2389    <div class="section" id="status:wd:element"><h3>This element is documented in a <strong>working
2390      draft</strong>.</h3>
2391        <p>The element is documented in a working or editor's draft
2392        and not yet completed.</p>
2393        
2394        <p>The element should not be used for any practical purpose.
2395        The feature might be drastically changed later or might be
2396        entirely removed.</p>
2397    
2398        <p>Most of new elements defined by HTML5 belong to this class.</p>
2399      </div>
2400    
2401    <div class="section" id="status:non-standard:element"><h3>This element is <strong>not part of any
2402      standard</strong> the conformance checker knows.</h3>
2403        <p>The element is not part of any standard or draft the conformance
2404        checker is aware of.</p>
2405        
2406        <p>The element should not be used for any practical purpose unless
2407        there is really a standard that defines the element.</p>
2408      </div>
2409    
2410    <div class="section" id="status:cr:attr"><h3>This attribute is in the
2411      <strong>call for implementation</strong> stage.</h3>
2412        <p>The attribute is in the call for implementation stage.</p>
2413        
2414        <p>Usually, using the attribute is safe.  However, it is a new feature
2415        so that it might not be implemented correctly.  If it is found that
2416        the feature is hard or impossible to implement, the feature
2417        might be revised, or in some case it might be dropped.</p>
2418      </div>
2419    
2420    <div class="section" id="status:lc:attr"><h3>This attribute is in the <strong>last
2421      call for comments</strong> stage.</h3>
2422        <p>The attribute is in the last call for comments stage.</p>
2423        
2424        <p>The attribute is relatively mature, though the standardization
2425        is not done yet.  It may be used for experiments.  Since it is a new
2426        feature, it might not be implemented correctly or at all.  If it is
2427        found that the feature is hard or impossible to implement, the feature
2428        might be revised or might be dropped.</p>
2429      </div>
2430    
2431    <div class="section" id="status:wd:attr"><h3>This attribute is documented in a <strong>working
2432      draft</strong>.</h3>
2433        <p>The attribute is documented in a working or editor's draft
2434        and not yet completed.</p>
2435        
2436        <p>The attribute should not be used for any practical purpose.
2437        The feature might be drastically changed later or might be
2438        entirely removed.</p>
2439      </div>
2440    
2441    <div class="section" id="status:non-standard:attr"><h3>This attribute is <strong>not part of any
2442      standard</strong> the conformance checker knows.</h3>
2443        <p>The attribute is not part of any standard or draft the conformance
2444        checker is aware of.</p>
2445        
2446        <p>The attribute should not be used for any practical purpose unless
2447        there is really a standard that defines the attribute.</p>
2448      </div>
2449    </section>
2450    
2451    <section id="langtag-errors">
2452    <h2>Language Tag Errors</h2>
2453    
2454    <div class="section" id="langtag:extension:duplication"><h3>There is another extension subtag
2455      <code><var>{value}</var></code>.</h3></div>
2456    
2457    <div class="section" id="langtag:extension:order"><h3>Extension subtag <code><var>{value}</var></code>
2458      is placed after subtag <code><var>{text}</var></code>.</h3></div>
2459    
2460    <div class="section" id="langtag:extension:unknown"><h3>Extension <code><var>{value}</var></code> is not
2461      defined when the conformance checker is written.</h3></div>
2462    
2463    <div class="section" id="langtag:extlang:case"><h3>Extended language subtag
2464      <code><var>{value}</var></code> is not in the preferred form, i.e. in
2465      lowercase.</h3></div>
2466    
2467    <div class="section" id="langtag:extlang:deprecated"><h3>Use of extended language subtag
2468      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2469      be undef) -->.</h3></div>
2470    
2471    <div class="section" id="langtag:extlang:prefix"><h3>Extended language subtag
2472      <code><var>{text}</var></code> is not allowed in the combination with this
2473      language (and extended language) subtag(s).</h3></div>
2474    
2475    <div class="section" id="langtag:extlang:invalid"><h3>Extended language subtag
2476      <code><var>{text}</var></code> is not registered.</h3></div>
2477    
2478    <div class="section" id="langtag:grandfathered:case"><h3>Language tag <code><var>{value}</var></code> is
2479      not in the preferred case combination.</h3></div>
2480    
2481    <div class="section" id="langtag:grandfathered:deprecated"><h3>Use of language tag
2482      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2483      be undef) -->.</h3></div>
2484    
2485    <div class="section" id="langtag:grandfathered:invalid"><h3>Language tag <code><var>{value}</var></code> is
2486      not a combination of RFC 4646 subtags and is not a registered grandfathered
2487      tag.</h3></div>
2488    
2489    <div class="section" id="langtag:illegal"><h3>Subtag <code><var>{value}</var></code> is
2490      syntactically invalid.</h3></div>
2491    
2492    <div class="section" id="langtag:language:case"><h3>It is a good practice to represent ISO 639-1
2493      language code <code><var>{value}</var></code> in lowercase.</h3></div>
2494    
2495    <div class="section" id="langtag:language:deprecated"><h3>Use of language subtag
2496      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2497      be undef) -->.</h3></div>
2498    
2499    <div class="section" id="langtag:language:invalid"><h3>Language subtag <code><var>{value}</var></code>
2500      is not registered.</h3></div>
2501    
2502    <div class="section" id="langtag:language:mul"><h3>Langauge tag <code>mul</code> should not be
2503      used.</h3></div>
2504    
2505    <div class="section" id="langtag:language:nosemantics"><h3>No semantics is defined for language subtag
2506      <code><var>{value}</var></code>.</h3></div>
2507    
2508    <div class="section" id="langtag:language:private"><h3>Language subtag <code><var>{value}</var></code>
2509      is a private use code.</h3></div>
2510    
2511    <div class="section" id="langtag:language:syntax"><h3>The language subtag <code><var>{value}</var></code>
2512      is syntactically invalid.</h3></div>
2513    
2514    <div class="section" id="langtag:language:und"><h3>Langauge tag <code>und</code> should not be
2515      used.</h3></div>
2516    
2517    <div class="section" id="langtag:private"><h3>It would be better if a private use language
2518      tag (<code><var>{value}</var></code>) is not used.</h3></div>
2519    
2520    <div class="section" id="langtag:privateuse"><h3>Private use subtag <code><var>{value}</var></code>
2521      is used.</h3></div>
2522    
2523    <div class="section" id="langtag:privateuse:case"><h3>Subtag <code><var>{value}</var></code> is not
2524      represented in the preferred case format.</h3></div>
2525    
2526    <div class="section" id="langtag:privateuse:syntax"><h3>Private use subtag <code><var>{value}</var></code>
2527      is syntactically invalid.</h3></div>
2528    
2529    <div class="section" id="langtag:redundant:case"><h3>Language tag <code><var>{value}</var></code> is
2530      not in the preferred case combination.</h3></div>
2531    
2532    <div class="section" id="langtag:redundant:deprecated"><h3>Use of language tag
2533      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2534      be undef) -->.</h3></div>
2535    
2536    <div class="section" id="langtag:region:case"><h3>It is a good practice to represent ISO 3166
2537      country code <code><var>{value}</var></code> in uppercase.</h3></div>
2538    
2539    <div class="section" id="langtag:region:deprecated"><h3>Use of region subtag
2540      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2541      be undef) -->.</h3></div>
2542    
2543    <div class="section" id="langtag:region:nosemantics"><h3>No semantics is defined for region subtag
2544      <code><var>{value}</var></code>.</h3></div>
2545    
2546    <div class="section" id="langtag:region:invalid"><h3>Region subtag <code><var>{value}</var></code>
2547      is not registered.</h3></div>
2548    
2549    <div class="section" id="langtag:region:private"><h3>Use of private use country code
2550      <code><var>{value}</var></code> is not allowed.</h3></div>
2551    
2552    <div class="section" id="langtag:script:case"><h3>Script subtag <code><var>{value}</var></code> is
2553      not in the preferred form, i.e. titlecase.</h3></div>
2554    
2555    <div class="section" id="langtag:script:deprecated"><h3>Use of script subtag
2556      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2557      be undef) -->.</h3></div>
2558    
2559    <div class="section" id="langtag:script:invalid"><h3>Script subtag <code><var>{value}</var></code>
2560      is not registered.</h3></div>
2561    
2562    <div class="section" id="langtag:script:private"><h3>Script subtag <code><var>{value}</var></code>
2563      is a private use code.</h3></div>
2564    
2565    <div class="section" id="langtag:script:suppress"><h3>Script subtag <code><var>{value}</var></code>
2566      should be suppressed when the language subtag is
2567      <code><var>{text}</var></code>.</h3></div>
2568    
2569    <div class="section" id="langtag:variant:case"><h3>Variant subtag <code><var>{value}</var></code> is
2570      not in the preferred form, i.e. lowercase.</h3></div>
2571    
2572    <div class="section" id="langtag:variant:combination"><h3>Variant subtag <code><var>{text}</var></code> might
2573      not be meaningful when it is used in combination with
2574      <code><var>{value}</var></code>.</h3></div>
2575    
2576    <div class="section" id="langtag:variant:deprecated"><h3>Use of variant subtag
2577      <code><var>{value}</var></code> is deprecated<!-- in favor of {text} (might
2578      be undef) -->.</h3></div>
2579    
2580    <div class="section" id="langtag:variant:duplication"><h3>Variant subtag <code><var>{value}</var></code>
2581      is specified twice.</h3></div>
2582    
2583    <div class="section" id="langtag:variant:invalid"><h3>Variant subtag <code><var>{value}</var></code>
2584      is not registered.</h3></div>
2585    
2586    <div class="section" id="langtag:variant:prefix"><h3>Variant subtag <code><var>{value}</var></code>
2587      cannot be used in this context.</h3></div>
2588    
2589    </section>
2590    
2591    <section id="rdfxml-errors">
2592    <h2>RDF/XML Errors</h2>
2593    
2594    <div class="section" id="bad-rdf-namespace"><h3>The namespace URI of an element that
2595      represents an RDF concept must be
2596      <code>http://www.w3.org/1999/02/22-rdf-syntax-ns#</code>.</h3></div>
2597    
2598    <div class="section" id="duplicate-rdf-id"><h3>The specified value is already used as an
2599      ID.</h3></div>
2600    
2601    <div class="section" id="duplicate-unqualified-attr"><h3>Both unqualified attribute and namespace‐qualified
2602      RDF attribute are specified, which is not allowed.</h3></div>
2603    
2604    <div class="section" id="parse-type-other"><h3>An invalid value is specified to
2605      the <code>parseType</code> attribute.</h3></div>
2606    
2607    <div class="section" id="second-node-element"><h3>There is another element, such that
2608      this element is not allowed.</h3></div>
2609    
2610    <div class="section" id="unqualified-attr"><h3>Unqualified attribute is not allowed.</h3></div>
2611    
2612    <div class="section" id="unqualified-rdf-attr"><h3>RDF attribute should be
2613      namespace‐qualified.</h3></div>
2614    
2615  </section>  </section>
2616    
2617  <section id="unsupported-messages">  <section id="unsupported-messages">
2618  <h2><i>Unsupported</i> Messages</h2>  <h2><i>Unsupported</i> Messages</h2>
2619    
2620  <div class="section unsupported" id="unsupported:attribute"><h3>This attribute is not supported by the  <div class="section" id="unknown-element"><h3>Conformance checking for element
2621    conformance checker; <em>it might or might not be conforming</em>.</h3>    <code><var>{local-name}</var></code> is not supported; <em>it might or
2622      <p>The conformant checker does not support the attribute.    might not be conforming</em>.</h3>
2623        <p>The conformant checker does not support the element.
2624      It cannot determine whether the document is conforming or not.</p>      It cannot determine whether the document is conforming or not.</p>
2625    </div>    </div>
2626    
2627  <div class="section unsupported" id="unsupported:element"><h3>This element is not supported by the  <div class="section" id="unknown-attribute"><h3>Conformance checking for attribute
2628    conformance checker; <em>it might or might not be conforming</em>.</h3>    <code><var>{local-name}</var></code> of element
2629      <p>The conformant checker does not support the element.    <code><var>{element-local-name}</var></code> is not supported;
2630      <em>it might or might not be conforming</em>.</h3>
2631        <p>The conformant checker does not support the attribute.
2632      It cannot determine whether the document is conforming or not.</p>      It cannot determine whether the document is conforming or not.</p>
2633    </div>    </div>
2634    
2635  <div class="section unsupported" id="unsupported:link-type"><h3>The link type <code>$0</code> is not standardized  <div class="section" id="unknown-link-type"><h3>Link type <code><var>{value}</var></code> is not
2636    or registered at the time of the release of the conformance checker;    standardized or registered at the time of the release of the conformance
2637    <em>it is non-conforming unless it has now been registered</em>.</h3>    checker; <em>it is non-conforming unless it now has been
2638      registered</em>.</h3>
2639      <p>The <code>rel</code> attribute is defined as a list of link types.      <p>The <code>rel</code> attribute is defined as a list of link types.
2640      Some common link types are defined in the HTML5 specification.      Some common link types are defined in the HTML5 specification.
2641      Additional link types can be registered to the WHATWG Wiki.      Additional link types can be registered to the WHATWG Wiki.
# Line 217  Web Document Conformance Checker (BETA)< Line 2646  Web Document Conformance Checker (BETA)<
2646      The link type might have been added to the registry since then.      The link type might have been added to the registry since then.
2647      In such case it might be conforming.  Otherwise, the      In such case it might be conforming.  Otherwise, the
2648      document is non-conforming.</p>      document is non-conforming.</p>
2649    
2650        <dl>
2651        <dt>Link types <code>shortcut icon</code></dt>
2652            <dd>Link type <code>shortcut</code> is not registered.
2653            Use only <code>icon</code> for linking to so-called favicon.</dd>
2654        </dl>
2655      </div>
2656    
2657    <div class="section" id="event-handler"><h3>Conformance checking for event handler attribute
2658      is not supported; <em>it might or might not be conforming.</em></h3></div>
2659    
2660    <div class="section" id="media-query"><h3>Conformance checking for media query
2661      is not supported; <em>it might or might not be conforming.</em></h3></div>
2662    
2663    <div class="section" id="addr-spec-not-supported"><h3>Conformance checking for an <code>addr-spec</code>
2664      is not supported; <em>it might or might not be conforming.</em></h3></div>
2665    
2666    <div class="section" id="XML-script-lang"><h3>Conformance checking for script
2667      language <code><var>{text}</var></code> is not supported;
2668      <em>it might or might not be conforming.</em></h3></div>
2669    
2670    <div class="section" id="XML-style-lang"><h3>Conformance checking for style
2671      language <code><var>{text}</var></code> is not supported;
2672      <em>it might or might not be conforming.</em></h3></div>
2673    
2674    <div class="section" id="atom|content-not-supported"><h3>Conformance checking for an Atom
2675      <code>content</code> element with <code>type</code>
2676      <code><var>{text}</var></code> is not supported.</h3></div>
2677    
2678    <div class="section" id="help-not-available"><h3>No more information is available.</h3>
2679        <p>No more information is available for this topic.</p>
2680    </div>    </div>
2681    
2682  </section>  </section>
2683    
2684  <d:catalog>  
2685  manakaiCompatMode:quirks;;Quirks Mode  
2686  manakaiCompatMode:limited quirks;;Limited Quirks Mode  
2687  manakaiCompatMode:no quirks;;No Quirks Mode  
2688    
2689  manakaiIsHTML:1;;HTML Document  
2690  manakaiIsHTML:0;;XML Document  
2691  </d:catalog>  
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2890    
2891    
2892    <div class="section" id="Error-level-m"><h3><a href="../error-description#Error-level-m" rel="help"><em class="rfc2119">MUST</em>‐level
2893            error</a></h3>
2894        <p>A violation to a hard requirement of the specification.
2895        The document is non‐conforming.</p>
2896      </div>
2897    
2898    <div class="section" id="Error-level-s"><h3><a href="../error-description#Error-level-s" rel="help"><em class="rfc2119">SHOULD</em>‐level
2899            error</a></h3>
2900        <p>A violation to a requirement of the specification.
2901        The violation might be legitimize in some case.  Otherwise,
2902        the document is non‐conforming.</p>
2903      </div>
2904    
2905    <div class="section" id="Error-level-w"><h3><a href="../error-description#Error-level-w" rel="help">Warning</a></h3>
2906        <p>A warning is an advice from the conformance checker
2907        to avoid solving a problem in a confusing or possibly wrong way.
2908        It does not affect to the conformance of the document, and
2909        may sometimes be inappropriate.</p>
2910      </div>
2911    
2912    <div class="section" id="Error-level-i"><h3><a href="../error-description#Error-level-i" rel="help">Information</a></h3>
2913        <p>An informational message just provides an additional information
2914        on the feature used in the document or the status of the retrieval
2915        or so on.
2916        It does not affect to the conformance of the document.</p>
2917      </div>
2918    
2919    <div class="section" id="Error-level-u"><h3><a href="../error-description#Error-level-u" rel="help">Not
2920          supported</a></h3>
2921        <p>Some feature that is not supported by the conformance checker
2922        is used in the document.</p>
2923      </div>
2924    
2925  <section id="license">  <section id="license">
2926  <h2>License of This Document</h2>  <h2>License of This Document</h2>
2927    
2928  <p>Copyright 2007 <a href="http://suika.fam.cx/~wakaba/who?">Wakaba</a></p>  <p>Copyright <time>2007</time>‐<time>2008</time>
2929  <p>This library is free software; you can redistribute it  <a href="http://suika.fam.cx/~wakaba/who?" rel="author" xml:lang="ja">Wakaba</a>
2930    <code class="mail">&lt;<a href="mailto:[email protected]">[email protected]</a>&gt;</code>.</p>
2931    
2932    <p>This document is free software; you can redistribute it
2933  and/or modify it under the same terms as Perl itself.</p>  and/or modify it under the same terms as Perl itself.</p>
2934  </section>  </section>
2935    

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