It's a link to an image, and the image is requiring login to be viewed, interesting that the login box is popping up on a site other than the image's origin
Looks like the image linked by daphz has since been made private by it's owner. I removed the image from the post so you should no longer get a pop-up in the thread. Thanks for bringing it to our attention!
Replies
http://www.polycount.com/forum/showpost.php?p=1596640&postcount=6
It's a link to an image, and the image is requiring login to be viewed, interesting that the login box is popping up on a site other than the image's origin