With the deluge of pop up’s and malicious malware, there are a few handy open source plugins available for firefox to stop you spending hours running malware scans and virus scans to destroy trojans and the like.

When visiting unknown and unfamiliar sites using firefox there is a clever little tool to prevent not only pop ups, but advertisements on sites http://noscript.net/ . This powerful tool prompts you the user to allow adverts and other embedded links to load mainly blocking scripting languages on the page like Javascript, reducing the risk of unauthorised downloads and unwanted adverts.
There is an initial learning curve where the users normal sites will require you to allow domains via the pop up menu provided, however, its a small price to pay for a solid security application.

Another complementary option to noscript is WOT (Web Of Trust), this tool essentially rates every site on the Internet for its security risk – green being all clear and safe, amber being worrisome and red a site to avoid.

With the above two tools your browsing experience should be a lot safer.