Another misbehaving adserver. I don't think it's any specific ad as I have gotten the popup with a different ad earlier, but in general the first forum link that I click opens a full screen ad, and it somehow remembers it so that I cannot repro the behavior again for a couple of hours. Edit: weird that I couldn't get the url shown in the a screenshot, when I tried to click on it, it turned into the url of the forum post I was going to... Edit: Got the url: Tech ARP Forums