It's a malicious ad, may not be a virus, but a possible bad browser addon. Clear the browser cache, history and remove potential malicious addons. If such is affected in all browsers, do a full anti-virus scan, if it's still around, search online for what it's possibly called and use an appropriate remover tool. There are more general cleaning or more specific remover tools out there, though one must be careful if such a tool could also contribute to a computers infection.
Finally there's add blockers to protect from such ad's in the first place, one such add on that has worked for me is uBlock Origin for FireFox. I find it works better that adBlock and without problems. As some anti-virus software flag it up as a potentially unwanted program.
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"When you begin to realize your own existence and break out of the social norm, then others know you have completely lost your mind." -PerfectlyDarkTails
AS 168/200, NT: 20/ 200, AQ=45 EQ=15, SQ=78, IQ=135