Ever go to a website and see highlighted text that, when your mouse rolls over it, pops up an advertisement? Obviously many sites use advertising to help pay for their sites, making it available to the public but there are times you really don't want them popping up all the time!
So, you can disable them. Roll over and look for the popup. Click the "?" and it will take you to the advertising company that manages the ads. Select disable and it will put a 'cookie' on your machine and the ads are gone.