It's not www.allyourbassonline.com. It's www.allyourbaseonline.com.
Anyway, I think I know what's going on here. All Your Base seems to be an online image gallery, among other things. It looks like in that thread, GamingFiend05 tried to post a picture, and I'm guessing that the picture was on an All Your Base gallery. It also seems that it was password protected, so when the browser tried to open the linked picture, it asked for the username and password. Just a guess though.