A website gave me a add-on/virus that makes ads pop up on my webpages, how do i get rid of them?

[Derek Kruk]

I recently started getting random ads on all my webpages. Like on twitter, There's a bar on top with adds and then a box above my profile setting with a ad. And also on facebook it shows up on the left and right margins. Also on Yahoo homepage, there is a rectangular box with three small ads that are clearly fake (Like "Loose 30 lbs fast!" and "New disease found in a town near you!").

It's clearly not by the sites themselves, it says under the ad box "Ads not endorsed by..." and then the name of the site im on.

I right clicked on it and then i clicked on a option that could take me to the source website. It turns out (im guessing here, it just seems like this) that i got the ads virus or add on from a page on knowyourmeme that i clicked on from another site.

Is there anyway i could either remove the virus (I rand a full scan and nothing showed up) or block all activity coming from Knowyoumeme (Like go to internet option - block site) or something like that?