A great list of WordPress cheat sheets.
http://lorelle.wordpress.com/2005/10/10/html-css-php-and-more-cheat-sheets/

Variables in CSS?

http://csshook.com/cssexamples/variables-in-css/

CSS Variables should be defined in an @variables at-rule. An @variable at-rule is composed of the ‘@’ character followed by the ‘variables’ identifier, optional target media types (separated by commas) and a block of variable definitions. The definition of a variable must precede all style rules contained or imported in the stylesheet.