Octet sequence {octets} is not an allowed representation of the character {char} — character reference {char:hexref} should be used instead.

No character is assigned to octet sequence {octets}.

Octet sequence {octets} is illegal.

The input stream is broken.

The input stream is encoded in ISO-2022-JP or its variant but is partially broken.

Note that an ISO-2022-JP stream must end in the ASCII state.

No character is assigned to octet sequence {octets}.

Character encoding {value} is not supported and the explicit character encoding specification is ignored. The result of the conformance checking might be wrong.

Character encoding {text} is not allowed for HTML document.

The character encoding used for the document is not allowed for HTML document. The document is non‐conforming.

Character encoding {text} should not be used for HTML document.

The character encoding used for the document is not recommended for HTML document. The document is non‐conforming unless there is any good reason to use that encoding.

Use of UTF-8 is encouraged (this document is encoded in {text}).

Use of UTF-8 as the character encoding of the document is encouraged, though the use of another character encoding is still conforming.

Conformance for character encoding requirements cannot be checked, since the input is not a byte stream.

The conformance checker cannot detect whether the input document met the requirements on character encoding, since the document is not inputed as a serialized byte sequence. The document is not conforming if it is not encoded in an appropriate character encoding with appropriate labeling.

There is no character encoding declaration.

The document does not contain a character encoding declaration. Unless the character encoding is explicitly specified in lower‐level protocol, e.g. in HTTP, or is implied by BOM, there must be a character encoding declaration. The document is non‐conforming.

The long character encoding declaration syntax <meta http-equiv="Content-Type" content="text/html; charset=charset-name"> is obsolete. The new syntax is:

<meta charset="charset-name">

Note that the encoding declaration in XML declaration has no effect for HTML document.

No character encoding metadata is found in lower‐level protocol nor is there BOM, while character encoding {text} is not a superset of ASCII.

The document is not labeled with character encoding name in lower‐level protocol, e.g. in HTTP, and the document is not begin with BOM. In addition, the character encoding of the document is not a superset of ASCII. The document is non‐conforming.

Unless there is a BOM, the character encoding for the document must be specified in e.g. HTTP‐level, as:

Content-Type: text/html; charset=charset-name

Existence of HTML character encoding declaration, i.e. <meta charset="charset-name">, does not allow to omit charset parameter for HTML document encoded in non‐ASCII compatible encoding.

Character encodings Shift_JIS, Windows-31J, and ISO-2022-JP are not a superset of ASCII for the purpose of HTML conformance.

Character encoding of this document is sniffed as {text} (Sniffed because no explicit specification for the character encoding of this document is found in the transfer procotol headers).

Character encoding of this document is defaulted to {text} because no explicit specification for the character encoding of this document is found in the transfer procotol headers.

Results might be wrong, since the conformance checker cannot find an appropriate decoder for the character encoding used for the document.

The conformance checker cannot find an appropriate decoder for the character encoding used to encode characters in the document.

This error is raised if:

• the conformance checker cannot find any decoder for the character encoding in use, but it knows that the encoding is similar to another character encoding, such that it uses the decoder for that character encoding, and therefore some octets might be interpreted incorrectly, or,
• the conformance checker find a decoder for the character encoding in use, but it does not know whether the decoder is conforming to the relevant specification or not, and therefore some octets might be interpreted incorrectly.

In either case, the result shown by the conformance checker might contain wrong errors caused by errorneous decoder or might not contain errors that should be raised if an appropriate decoder is used.

Conformance error checking for the character encoding {text} is not supported.

Sniffed character encoding {text} is same as the character encoding specified in the character encoding declaration. This is not an error.

While parsing the document as {text}, a character encoding declaration specifying a different character encoding is found. The document is reparsed.

While parsing a document in a character encoding, a character encoding declaration which declares the character encoding of the document as another character encoding is found. The occurence of this warning itself does not make the document non‐conforming. However, the failure of the first attempt to to detect the character encoding might be a result of non‐conformance of the document.

The document will be reparsed from the beginning. Some error or warning might be reported again.

These are suggestions to avoid this warning:

• Specify charset parameter in the Content-Type field in the HTTP header, as:

  Content-Type: text/html; charset="charset-name"

• Put the character encoding declaration (<meta charset="charset-name">) just after <head> start tag.
• Use UTF-8.

The NULL character is not allowed.

Code point {text} is not allowed.

Noncharacter {text} is found in the input stream.

Noncharacter code points are used in the input stream.

Noncharacter code points are reserved for internal processings. Their use for information interchanges are forbidden.

In addition, they are not allowed in HTML document.

Character {text} is not a Unicode character.

Use of character {text} is deprecated.

Use of character {text} is discouraged.

Code point {text} is not the preferred representation of that character.

Character {text} should not be used in many cases.

Attribute name cannot contain characters ", ', and =.

Attribute value must be quoted by " or ' if it contains a ", ', or = character.

In an unquoted attribute value, a character " (U+0022 QUOTATION MARK), ' (U+0026 APOSTROPHE), or = (U+003D EQUAL SIGN) is contained. These characters are not allowed in unquoted attribute values, since they are used to quote attribute values or to separate attribute name and value.

This error is also raised if one try to use empty attribute value like <foo bar= baz=>; in this example, baz= is treated as an invalid attribute value for the attribute bar, not as another attribute.

The & character must be escaped as &.

An & character which is not part of any reference appears in the input stream. The document is non‐conforming.

Any & character in URI (or IRI) must be escaped as &.

The & character must be the first character of a reference:

Named entity reference

&entity-name;

where entity-name is the name of the character entity to be referenced.

Numeric character reference

&#d;

where d is the decimal representation of the code position of the character to be referenced.

Hexadecimal character reference

&#xh;

where h is the hexadecimal representation of the code position of the character to be referenced.

To represent & as a data character, use named entity reference:

&

A </ string is not followed by a tag name.

There is a < (U+003C LESS-THAN SIGN) character immediately followed by a / (U+005F SOLIDUS) character, which is not part of any end tag, in the input stream. The document is non-conforming.

The </ sequence immediately followed by an EOF is interpreted as a string data of </.

The </ sequence as string data must be escaped as:

</

A < character is not followed by tag name or by a ! character.

A < (U+003C LESS-THAN SIGN) character which is not part of any markup appears in the input stream.

The < character as a data character must be escaped as:

<

The decimal representation of the code position of a character must be specified after &#.

An & (U+0026 AMPERSAND) character immediately followed by a # (U+0023 NUMBER SIGN) character which is not part of any reference appears in the input stream. The document is non-conforming.

The string &# must be the first two characters of a reference: