Most browsers has a built-in pop-up blocker. Here's how to turn it on
-Click on the Tools menu
-Click Internet Options
-Click Privacy Tab
-Check the box that says "Block pop-ups"
-Click Ok to exit
-Click on the Firefox button (Tools menu in XP)
-Select the Content panel
-In the Content panel, check the "Block pop-up window"
*In the Exceptions button. A dialog will appear that shows all the sites that are allowed to show pop-ups. If the site that's opening pop-ups is in the list, select it and press Remove Site. Click Close
-Click OK to close the Options window.
-Click the wrench Icon
-Go to "Under The Hood" Tab
-Under "Privacy" click "Content Settings"
-Click pop-ups on the side
-Choose to block pop-ups
If you still see pop-ups, do a system scan for viruses, spywares or malwares.
CLICK HERE if you don't have any antivirus installed in your pc.