Re:been seeing this a while (Score 1)

Yes, it appears to be a Flash clip that open the pop-unders.. Internet Explorer's pop-up killer blocks these pop-unders, but Mozilla 1.0 with the Flash plugin does not. To avoid them, you can install the Flashblock plugin for Mozilla. It is also possible to bypass many of the pop-up blockers using a Java applet, but I think the advertisers avoid Java due to its slow initialization.