It seems that you have an add-on installed which annoys you with browser pop-ups. In this case, I recommend checking the add-on gallery (Tools > Add-ons in Firefox, Menu > Tools > Extensions in Chrome and Tools > Manage add-ons in Internet Explorer).
On the other side, it's likely that your computer is infected with malware. If so, you should run an anti-malware application. I recommend using Spybot Search'n'Destory or Malwarebytes Anti-malware.
No matter what the option you choose, perform a full scan of your computer after you update the databases to the latest version in order you get sure that the possible threats are removed successfully.