My buttons fail.. UhG!

Ok, I know that you guys are great with answering questions and all that jazz, so I figured I’d ask you all first. Ok, If you’ve ever seen on those webpages, such as www.tvulive.com or www.tombraider.com that have the little flash things, that when you put your mouse over them, a little dropdown box appears below the button and if you keep your mouse on the button, or the stuff that droppeddown, it doesn’t go back up. Can someone please explain how to do this… I’m not even sure on how to make stuff move wheny ou use a button, only like change colors and junk. It would be great if someone could help. Thanks