by coco moco July 29th 2011, 2:08 am
If you don't make a sprite out of it, you will find it very laggy on first load. The second image won't show - it will just be blank - until you move the cursor back over it. Sprites do work on the navigation bar, although, buttons don't seem to respond at all.
A trick I've found that isn't laggy, is to increase the opacity on hover. You can apply it to lists, so navbars and all the buttons you want will work.
Furthermore, if you get the buttons to work as a sprite, and I never could, the opacity command cuts the sprite in half and makes things a lot faster.
I would highly recommend against using 2 images, though, unless you're using jscript, which will preload on the page opening (a sprite without spriting client side, but still with all the extra server requests).