i'm having the same problem. php is a ubiquitous web page format (e.g. these forum pages), so i don't understand why it's doing that. it prompts you to download home.php from m.facebook.com (!) so it looks like facebook is doing a browser/agent check and redirecting us to the cell-phone-ized version of the website. wtf?

i haven't tried fennec or iceweasel. anyone else?