I’m looking for an authoritative source on which browsers people browse facebook with. Specifically, I’m curious what percent IE6 and IE7 are at.
I constantly run into issues with IE7 on Facebook, and am trying to determine if it’s worth my time to search for solutions.
I doubt if Facebook would release that private information.
You could use your own web server’s log files (the server that hosts your facebook app) and get stats from those files. But I presume, you don’t have access to those. So you might be able to make a guess by checking out the global stats here: http://www.w3counter.com/globalstats.php or http://www.w3schools.com/browsers/browsers_stats.asp
EDIT
Some information from a hosting company about its Facebook stats. However, this information is from 2009. 😐
https://www.facebook.com/note.php?note_id=94523840758