You posted with a very old Firefox 3.0.0.15 version in the user agent.

Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.0.15) Gecko/2009101601 Firefox/3.0.15 FBSMTWB

You can see the Firefox version at the top and the user agent at bottom of the "Help > About" window (Mac: Firefox > About Mozilla Firefox). You check (compare) what websites see: http://whatsmyuseragent.com/ - Whats My User Agent?

You can check the general.useragent prefs on the about:config page. You can open the about:config page via the location bar, just like you open a website. Filter: general.useragent If general.useragent prefs are bold (user set) then you can right-click that pref and choose Reset.

See Web sites or add-ons incorrectly report incompatible browser and Find what version of Firefox you are using See also http://kb.mozillazine.org/Resetting_your_useragent_string_to_its_compiled-in_default

No matter what version of Firefox, it regularly bombs out with Facebook, even crashes computers when you try to use them together. People are starting to get fed up with this regular, annoying incompatibility of two of the top players....

I downloaded the new Firefox, and now Facebook won't open. It just says " (GIF Image, 1x1 pixels) " on the tab. Blank page. Is there anyway of getting the last version of Firefox back?

Some firewalls like Kaspersky can block content and send a 1x1 GIF image instead. Kaspersky": "Protection > Firewall > Filtration system: disable the "Banner Ad Blocker"

See Configuring Kaspersky Internet Security and Configure firewalls so that Firefox can access the Internet

I suddenly can't use facebook. it opens but freezes and i have to shut FF down. I hate it i love FF and i am on faceboo all the time is there a way to get around this isssue or fix it maybe getting an old version of firefox? pleaaaaaaaaaaaaaase help

Let's stop the crock and tell it like it is: Firefox is beginning to suck. I have used FF for over two years now, with Facebook... now it has bombed BIG-TIME! I have had to go back to IE because the new Facebook update of October, 2011, will NOT work with Firefox.... well, it takes 20 seconds to load, freezes up constantly.... or crashes. Also, I have the supposed latest and greatest version of Firefox! Finally, I have high speed internet with a mega-fast computer... with an i7 chip, 18 GB of RAM, and Geforce 470 1GB video card! So.... what's up Firefox?! Back to Internet Explorer we are all now "forced" to go. :-(

For the record, I have used various versions of Firefox (currently 6.0.2) for as long as I've been on Facebook (just under three years), and have had no trouble. Any troubles I've had were usually due to time-outs (i.e., it took me a long time to enter the wall message or reply) or a glitch on my end (e.g., loose modem/DSL cable, etc) or not refreshing my browser window or posting in an unintended area (i.e., someone else's wall by mistake), etc.