hello madmats2, this is likely caused by adware and malicious software already present on your system. please perform all these steps: # [[Reset Firefox – easily fix most problems|reset firefox]] (this will keep your bookmarks and passwords) # afterwards go to the firefox menu ≡ > addons > extensions and in case there are still extensions listed there, disable them. # finally run a full scan of your system with different security tools like the [http://www.malwarebytes.org/products/malwarebytes_free free version of malwarebytes] and [http://www.bleepingcomputer.com/download/adwcleaner/ adwcleaner] to make sure that adware isn't present in other places of your system as well. [[Troubleshoot Firefox issues caused by malware]]

'''[https://addons.mozilla.org/en-US/firefox/addon/adblock-plus/ Adblock Plus]''' {web link} Blocks annoying video ads on YouTube, Facebook ads, banners and much more. Adblock Plus blocks all annoying ads, and supports websites by not blocking unobtrusive ads by default (configurable).