[newsio]

Excellent little demo.

Shows how long I've been out of touch with CSS. Didn't know stuff like variables or rounded edges was supported.

[pohl]

The variables appear to be a SASS construct, not CSS.

http://en.wikipedia.org/wiki/Sass_(stylesheet_language)

[imathis]

SASS compiles to CSS.

[smanek]

And it inlines the variables as constants at 'compile time'.

[ned]

Rounded corners are supported in Webkit Gecko and Presto, and not in Trident of course.

Variables are provided by SASS, a CSS pre-processor language/framework.