I'm having a popup box come up...

Whenever I try to view anything in video format online, I get a box that says "Adobe Flash Player settings: local storage d.yimg.com is requesting permission to store information on your computer" It has an "allow" and a "deny" button at the bottom,but if you hit "deny" nothing happens, and it just continues to sit there.

Does anyone know how to get rid of this? I believe one of my kids may have clicked on something while on a game site, and that is why it is even here.

Any help is much appreciated!