Adult friend finder banner coming up on my browser!!!

Hi all,

Please help.. There's this banner having obscene content that  leads to the site adultfriendfinder.com. It pops up on places where an image or video should come up.

 

eg:- like if i load up video on facebook , im able to stream for a while but after some time the video stops playing and the banner comes in its place( all play buttons of the flash player disappear) and the banner says do you want to f**k her!!

 

Please help get this out of my laptop!! my young sister accesses this laptop! its embarrassing ,

 

 

thanx

SAM