1. It is not a "pop-up", but a redirection. (Like it was trying to send you to another page, except that the page isn't there).
2. Only on the main page (with the forums listed): http://www.flyertalk.com/milesfr.shtml
3. See above. Only that page.
I'll try cleaning out cache, but I do get a refreshed page when I go to that page. (Updated with last posts, for example).

Thanks for looking at this. As my original post said, not a big problem, but an annoyance.

Lee W.