Why do I have popups (ads) appearing on top of my sites?

[Jimmy]

Recently I have kind of ad popups appearing from nowhere at the top of sites. I happened to be on an adobe site, youtube, facebook, which usually doesnt have. What is the problem and what should I do? Is it a virus, is my computer infected by any kind of threat?
I'm scanning right now, I'll tell you guys if it changed something

[Michael]

what do the popups say.
scan with malwarebytes and spybot

[jim w]

sounds like you have adware and that's a type of spyware. superantispywhere is a good free program that should get rid of it.
review and download here scroll down
http://www.techsupportalert.com/best-fre...emover.htm

[Cheeky]

delete your cookies and temporary files on and off line and see if this clears it then get a popup stopper, run a virus scan and do the normal things to clean up your system

[Gerry Attric]

Sounds like your computer is infected with adware. They usually hamless, just annoying. Try running Ad-Aware (the free version) - that should get rid of those annoying pop-ups.