The popups are generated by 'spybots' in your computer. They are programs that track down your IP address and flood your computer with popups once you enter a specific site.
You normally get spybots from shareware sites and bogus porn sites ^_^;
They install themselves in your computer without warning which makes them hard to detect ;_;
Most peoples computers get infected by spybots and they don't have a clue whats going on, which diminishes their internet surfing pleasure.
Go here to download Spybot search and destroy ^_^
http://security.kolla.de/