ad.doubleclick.net is technically "spyware"- they are an "ad server" that places cookies on your computer (usually without you knowing about it). The next time you go to a site with a doubleclick.net banner, it reads your cookie and starts tracking your activity (last site visited, length between visits, etc.) Eventually, they will have an entire history of where you have been. Look at the URL listed in the above post (#5)- that URL shows that doubleclick.net has set up a special folder just to handle their ads to Renderosity. So, they probably have some programs at their end that track how many times the URL has been accessed and when. They match the "timestamp" to someone's cookie, and they're off and tracking you. 1) Everyone absolutely needs to be running some kind of ad-blocking software: Ad-Subtract, AdWasher, etc. (Go to www.downloads.com and do a search.) These programs will block cookies AND pop-up ads. 2) I certainly hope that Renderosity has not sold ad space to spyware companies like doubleclick.net and that this is a one-time banner.