Why do I keep (all of a sudden) seeing these ads on my search engine and youtube and facebook?

This JUST started happening recently, i ran AVG antivirus but its not detecting anything... These ads keep coming up on different pages, like "Mom turns skinny in 4 weeks." ad, and the others as follows in the links below:

http://postimg.org/image/ioow8l5ln/\

http://postimg.org/image/prw9h2ziv/

http://postimg.org/image/94onoeb8j/

?2013-04-16T07:49:01Z

Favorite Answer

If you're using Chrome, I believe it's a extension. I forgot what it's name is but it constantly brings up these weird ads. Go to your extensions and remove everything.

option >> tools >> extension