pop up prob. Maybe?

All of a sudden when I click on a site or predominantly on something like a thread in a forum, I get the address in the bar and also a second address to the right and up pops an add for something.

When I click on the popped up side X in the address bar it will close and the place I wanted to got to will appear.

This is a new deal for us and surely can be remedied.

Advice will be appreciated.