InterCosmos

Special thanks to Bill Webb for sharing this tip along with many more on his site:
Counterexploitation and the Free Webpage Provider.

There is not really a good way to eliminate the Popup ads, because they are different each time the server creates them. This means, that unlike most other places, you can't have one script that kills the popup ads. But, they do offer you the choice between ad frames, banners, or popups. Simply choose the "Ad frame" option from your preferences like so:

Then, use the Javascript to break out of frames to prevent your page from getting stuck in the ad frame. Or, if you don't mind the banners, just leave those in your page to prevent the Popup ads.