I know, it's really annoying. The way to fix it is right when you hear it click your refresh/reload button on your web browser. You don't lose anything on the web site and it loads a new ad and rarely will the same ad load two times in a row (if it does, then refresh again).
Well if it weren't for those stupid ads, this site wouldn't be as good as it is because those annoying ads help pay for the site, to keep it going. You can get less ads like the annoying ones by signing up for memberships? So Stop complaining, just refresh or click onto a different thread.