I'm so fed up with pop unders in Safari that I'm going to download Firefox and give it another try. There is a program called PithHelmet that does block these flash ads, but it's not free and wouldn't install on my machine. Hopefully Apple deals with this problem in Tiger and gives users the option to turn flash off. Even Internet Explorer for Windows XP SP 2 has a better ad blocker than Safari. Meanwhile, Macromedia has a nice guide on how to make pop ups, pop unders, and other annoying advertisements.