Yahoo altfarm.mediaplex Error Code -12263

Add altfarm.mediaplex.com to your hosts file.

Seems like you created it yourself, as you stated below:

Sh... why do you do such nonsense?

He did. However, if he had not already done so, it would a bad advice. As if these funny descriptions wouldn't be obviously idiotic enough...

Sebastian is right. It's your fault. But not for the reasons he stated.

Both Yahoo and Ebay are well known for spying on users and feedind personal information back to the offshore mediaplex conglomerates.

Mediaplex, a British consortium, pays Yahoo a tenth of a penny for your private habits. Think about that.

Your privacy is only worth one tenth of a red cent to them. Do a search for "Mediaplex removal tool" or "Kill MediaPlex Now" to remove the registry keys that cause these problems.

If you were running adaware or spyware blaster, you'd not be bothered by these yahoo trojans.

It's really all your fault as Sebastian said.

Interesting what people claim to be well known, even though nobody actually knows it, because it's simply wrong.

Yahoo and eBay are sell ad-space by including Mediaplex stuff. Nothing else. They don't aqquire or feed any information - this is what you explicitly have to do.

WTF? He actually installed some of this stuff? If so, "removal tools" would be another dumb idea. The system was compromised, and you need to flatten and rebuild.

But it seems like you got the technical perspective all wrong. A webbrowser opening a popup is nothing special, and displaying an error message for a self-initiated error isn't anything special either. I fail to see why you assume that anything got installed.