In website design image rollovers are always a big deal. While I mostly use unobtrusive javascript for rollovers, others seem to prefer CSS sprites. I really like the idea of sprites in that it is a fully css approach, I don’t like the hassle of building the combined images. Also with the unobtrusive javascript implementation, you can just create new images and your rollover effect is in place assuming you use some kind of naming convention that allows you to find all the appropriate images and create the on/off states.