Hey, for the last few weeks the websites I frequent have been getting filled with ads. Ads imbedded in text, others at the top, side and bottom of the screen, still others would pop up when I'd hover my mouse over a thumbnail image. It took me a while, but I traced it to an add-on called Youtube HD plus. If you have this add-on, whether or not you installed it (because I sure didn't and it was there anyway), get rid of it. It's nothing but adware.