Whats with these little thumbnail adds I see popping up on the forum????

I think you have some malware if you are seeing anything other than the normal banner or signature ads

Yup. Malware. Scan your computer.

Ha! I was expecting a new way to do addition or something.

when the cursor hits one of the under scored words then you get the ads. i thought it might be another unwanted xfinity feature.

I had the same thing about a month ago, its some kinda virus. It went away after a good cleaning.

Subtracts

I think they multiply ...

Exponentially.

Really nasty ones will do Fourier series and spherical harmonics...

Yep I had malware in the computer, cleaned it all out, now back to normal...

Mine wasn't a virus.
I bought a new NetBook and while I was installing new software something called Sidekick Shopper or something like that was installed.
It creates hyper text out of given words I assume.
So when the mouse crosses over the word, the ad pops up.

Just uninstalled it and the problem went away.

But that's after about 5 hours of installing and running Ad Aware and SpyBot about 4 times each.

Some would disagree...annoying, unwanted software might as well be a virus, even if it is easily uninstalled

Mine was a coupon popup. Not a virus or malware. Found it under the browser add on list. This is probably new that bypasses search and kill programs.
Look super close when it pops up and google How to remove...
Worked for me.