How can I get my internet browser's back button to work again?

Every time I try to go back a page, the button "indents" when I press it, but nothing happens! It's been like this for a few months, and I eventually figured out that if I close all my open internet windows and bring them up from fresh then it would work. However, I just tried doing this when the back button yet again failed to work, and it didn't fix the problem! I have Windows 7, so if someone could tell me what's wrong and give me a step-by-step on how to fix it, that would be much appreciated!