Variables have been a much wished-for addition to CSS for a long time. Yesterday, Mozilla was the first browser maker to add support for them, in its latest Firefox Nightly. I played around with it for a bit, trying to come up with uses for them, apart from the most obvious (making colors, font-sizes etc more DRY). These thoughts are very unfinished, and possibly stupid. But hey, I guess it'll be a while before we see enough browser support for these to make them useful, so we have time to iron out the kinks.
Read the whole post "Playing around with CSS variables - "custom properties""