In these cases, you can use AdBlock Plus, an extension for Mozilla Firefox, that lets you block any adverts on the websites you're visiting in real time.
This often brings about a drastic improvement in your browsing experience, especially on pages full of ads. To block different advertising areas, you can do it manually with the right mouse button, or download a readymade filter from the Internet.
This second method is often faster and more effective than the first, and is the first option that will be presented to you when AdBlock Plus is installed.
If you want to get rid of intrusive web advertising forever, you should definitely use AdBlock Plus.