     |
& [&]
Constraint: The ampersand character MUST NOT appear in its literal form, except when used as markup delimiter, or within a comment, a processing instruction, or a CDATA section.
< [<]
Constraint: The left angle bracket MUST NOT appear in its literal form, except when used as markup delimiter, or within a comment, a processing instruction, or a CDATA section.
> [>]
Constraint: The right angle bracket (>) MAY be represented using the string ">", and MUST, for compatibility, be escaped using either ">" or a character reference when it appears in the string "]]>" in content, when that string is not marking the end of a CDATA section.
" ["]
Constraint: To allow attribute values to contain double quotes, the double-quote character (") MAY be represented as """.
' [']
Constraint: To allow attribute values to contain single quotes, the apostrophe or single-quote character (') MAY be represented as "'".