Cascading Style Sheets, Level 2 - World Wide Web Consortium

4.3.9 Frequencies
Frequency values (denoted by in the text) are used with aural
cascading style sheets [p. 277] .
Their format is a immediately followed by a frequency unit identifier.
Frequency unit identifiers are:
Hz: Hertz
kHz: kilo Hertz
Frequency values may not be negative.
For example, 200Hz (or 200hz) is a bass sound, and 6kHz (or 6khz) is a treble
sound.
4.3.10 Strings
Strings can either be written with double quotes or with single quotes. Double
quotes cannot occur inside double quotes, unless escaped (as ’\"’ or as ’\22’).
Analogously for single quotes ("\’" or "\27").
Example(s):
"this is a ’string’"
"this is a \"string\""
’this is a "string"’
’this is a \’string\’’
A string cannot directly contain a newline. To include a newline in a string, use
the escape "\A" (hexadecimal A is the line feed character in Unicode, but represents
the generic notion of "newline" in CSS). See the ’content’ property for an
example.
It is possible to break strings over several lines, for aesthetic or other reasons,
but in such a case the newline itself has to be escaped with a backslash (\). For
instance, the following two selectors are exactly the same:
Example(s):
A[TITLE="a not s\
o very long title"] {/*...*/}
A[TITLE="a not so very long title"] {/*...*/}
4.4 CSS document representation
A CSS style sheet is a sequence of characters from the Universal Character Set
(see [ISO10646]). For transmission and storage, these characters must be
encoded by a character encoding that supports the set of characters available in
US-ASCII (e.g., ISO 8859-x, SHIFT JIS, etc.). For a good introduction to character
sets and character encodings, please consult the HTML 4.0 specification
([HTML40], chapter 5), See also the XML 1.0 specification ([XML10], sections 2.2
and 4.3.3, and Appendix F.
When a style sheet is embedded in another document, such as in the STYLE
element or "style" attribute of HTML, the style sheet shares the character encoding
of the whole document.
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