I just passed this by my white hatted, 'network security handy' friend. He dug into it and it seems that this is a simple issue of akamai.net (a well established content delivery company) using a certificate that has Facebook's name in it, instead of theirs. Nothing to worry about, as far as he can tell.
More specifically, he says "it is probably an akamai ad hoping you're an iPad user with Safari instead of the Facebook app.
It probably is an add for you to download the FaceBook app IF you are using Safari with an iPad....It's a setup error. It's a BAD setup error that makes Akamai look like dummies."
It looks like the issue may already have been resolved, server-side.
Thanks.. I was curious and worried as I did not have this problem before. I get into Hong Kong and the second day on wifi I start getting this every time I switch tabs,refresh a page or open a new page up. Very irritating because it just keeps popping right back up in the middle of the screen.
Never ever did trust Facebook so I did not download their application onto my iPad.