What can I do to stop small windows at the bottom of the page from staying open in Firefox.?

Let's see if I can describe this. Right now, I'm looking at two Firefox (latest version) windows with the same information, one big normal one, and one small one (1"x1 1/2"), at the bottom of the page, just above one of the two tabs (maybe they aren't called that) at the bottom of the page. If I move my mouse to be over the other tab, I will see a different small window, showing the contents of that page, while I continue to see this big one. The problem is that if I move my mouse away from both tabs, one of the small windows remains open, blocking my view. It's annoying. What can I do?