Originally Posted by fancyfootwork15
Delete your cookies and cache. Then if you haven't already switch to a fresh version of Firefox or Chrome.
Make sure Flash, etc. are updated. Some of the ads here (and elsewhere) use Flash. If it's a poorly written ad, bugs in the ad can cause issues with the browser window. Newer versions of Flash help with this, but of course, new bugs are constantly being introduced, too, so it's a never-ending update race.
If it keeps happening after all of this, check for updates to things like your graphics drivers. I know that sounds odd, but I'm currently stuck on a buggy graphics driver version on my Windows box at work. The graphics driver will cause various issues, from browser windows (particularly in Chrome) not scrolling correctly, to a full-on graphics driver crash, where all screens will go blank for a couple of seconds, and then reset themselves (thankfully, Windows can at least restart the graphics driver these days. In older versions of Windows, that would have required a reboot to correct).