CSS coding for non stationary thumbnails

Can coding of thumbnails in css to a larger picture be not stationary. Meaning if your thumbnails and location of the larger picture will move up or down the page depending on how much information is on the page generated by a database. The thumbnails will always at the bottom of the page and the larger image to show above it I want to use the mouseover function instead of creating a new window with the larger image.

Is http://javascript.about.com/library/blroll1.htm the sort of thing you are looking for?

Thanks for the pointer. I see that javascript is the way to go instead of style sheets, which I figured probably it would be.