Description of Errors

HTML5 Parse Errors in Tokenization Stage

Tag <$0> is not allowed after the end tag </html>.

The start or end tag of an element appears after the html element has been closed. The document is non-conforming.

Any content of the document other than comments must be put into the html element.

 Tag <$0> is not allowed after the end tag </body>.

The start or end tag of an element appears after the body element has been closed. The document is non-conforming.

Any content of the document other than head contents and comments must be put into the body element.

 The & character must introduce a reference.

An & (U+0026 AMPERSAND) 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 &amp;.

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: 

&amp;

 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: 

&lt;/

 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: 

&lt;

 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:

Numeric character reference
&#d;
where d is the decimal representation of the code point of the character to be referenced.
Hexadecimal character reference
&#xh;
where h is the hexadecimal representation of the code point of the character to be referenced.

To represent &# as data characters, use a named entity reference for the & character: 

&amp;#

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

The string &#x or &#X which is not part of any reference appears in the input stream. The document is non-conforming.

The string &#x or &#X must be the first three characters of a hexadecimal reference: 

&#xh;
where h is the hexadecimal representation of the code point of the character to be referenced.

To represent &#x as data characters, use a named entity reference for the & character: 

&amp;#x

 String <! is not followed by --.

There is a < (U+003C LESS-THAN SIGN) character followed by a ! (U+0021 EXCLAMATION MARK) character, which is not followed by a -- or !DOCTYPE. The document is non-conforming.

Comments
In HTML documents, comments must be introduced by <!-- (<! immediately followed by two -s) and must be terminated by -->. Strings <! not followed by -- and <!- not followed by - are not valid open delimiters for comments.
Marked sections, including CDATA sections
Marked sections are not allowed in HTML documents.
Markup declarations
Markup declarations, except DOCTYPE and c