Cascading Style Sheets, Level 2 - World Wide Web Consortium

The second declaration on the first line has an invalid value ’12pt’. The second
declaration on the second line contains an undefined property ’font-vendor’. The
CSS2 parser will ignore [p. 42] these declarations, effectively reducing the style
sheet to:
H1 { color: red; }
P { color: blue; font-variant: small-caps }
EM EM { font-style: normal }
4.1.9 Comments
Comments begin with the characters "/*" and end with the characters "*/". They
may occur anywhere between tokens, and their contents have no influence on
the rendering. Comments may not be nested.
CSS also allows the SGML comment delimiters ("") in certain
places, but they do not delimit CSS comments. They are permitted so that style
rules appearing in an HTML source document (in the STYLE element) may be
hidden from pre-HTML 3.2 user agents. See the HTML 4.0 specification
([HTML40]) for more information.
4.2 Rules for handling parsing errors
In some cases, user agents must ignore part of an illegal style sheet. This specification
defines ignore to mean that the user agent parses the illegal part (in
order to find its beginning and end), but otherwise acts as if it had not been there.
To ensure that new properties and new values for existing properties can be
added in the future, user agents are required to obey the following rules when
they encounter the following scenarios:
Unknown properties. User agents must ignore [p. 42] a declaration [p. 41]
with an unknown property. For example, if the style sheet is:
H1 { color: red; rotation: 70minutes }
the user agent will treat this as if the style sheet had been
H1 { color: red }
Illegal values. User agents must ignore a declaration with an illegal value.
For example:
IMG { float: left } /* correct CSS2 */
IMG { float: left here } /* "here" is not a value of ’float’ */
IMG { background: "red" } /* keywords cannot be quoted in CSS2 */
IMG { border-width: 3 } /* a unit must be specified for length values */
A CSS2 parser would honor the first rule and ignore [p. 42] the rest, as if the
style sheet had been:
IMG { float: left }
IMG { }
IMG { }
IMG { }
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