CSS vs Javascript for behavior

As I became more comfortable with Javascript and started using Ajax on a regular basis, I found myself moving elements of interactivity out of my stylesheets and into my Javascript. This not only made sense to me (to keep all interactivity code in the same place), but it made browser consistency much easier for me and kept my stylesheets much lighter and cleaner.

Chris Heilmann gives a thorough run through of the history, pros and cons of this battle.