CSS allows Unicode characters to be entered by number. For example, if a CLASS value in some Russian document contains Cyrillic letters `EL' `PE' (Unicode numbers 041B and 041F) and you want to write a style rule for that class, you can put that letter into the style sheet by writing
.\041B\041F {font-style: italic }
This works on all keyboards, so you don't need a Cyrillic keyboard to write CLASS names in Russian or another language that uses that script.
The digits and letters after the backslash (\) are a hexadecimal number. Hexadecimal numbers are made from ordinary digits and the letters A to F (or a to f). Unicode numbers consist of four such digits.
If the number starts with a `0', you may omit it. The above could also be written as
.\41B\41F { font-style: italic }
But be careful if the next letter after the three digits is also a digit
or a letter a to f! This is OK: .\41B-\41F, since the dash (-)
cannot be mistaken for a hexadecimal digit, but .\41B9\41F is only two letters,
not three.
Four digits is the maximum, however, so if you write
.\041B9\041F { font-style: italic }
that's three letters: two Cyrillic ones with a `9' in between.
Unicode numbers can be found in the Unicode book: The Unicode Standard version 2.0, Addison Wesley Developers Press, Reading, Massachusets, 1996, ISBN 0-201-48345-9.
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