Hello, last night I updated the Facebook App & now it will not load? It opens, & then shuts after around 2-3seconds. I have deleted & re-installed, but still the same. Please can soneone help!
No no... you won't loose anything from your iPhone. A hard reset is holding the Home & Lock buttons together at the same time for approxiamtely 10-15 seconds. Your screen will go black (if you're on iOS 5.1.1 or lower the "slide to power off" will appear before going black, disregard it)... continue holding both buttons. When the Apple logo appears release both buttons... your iDevice will reboot back to the lock screen.
You can find your iOS version under Settings.app -> General -> About
As for the Facebook app crashing, I've had the exact same problem since Facebook v5.2.1, and no matter how I delete it or remove it and reinstall it, it still crashes as well. The only way I got the problem fixed was to manually delete all the stationary and temporary files related to Facebook.app, and install an older version of Facebook which I got from my developer access. I know that it's having problems with jailbroken devices as my 4S and old 3GS can't run it, but my 6.0.1 4S and 6.0.2 5 run it perfectly.
I wished I wouldn't of updated now  it's a nightmare using Facebook on Safari. My phone isn't jailbroke, is there anyway I could get the old version of Facebook back? I haven't got a clue about all this technical stuff, ha! & I don't fancy paying just
too get Facebook back 
There are only 3 ways of installing an older version of an app to a phone.
Method 1: You'll need developer access and download the older version of the app and install it to your phone. This requires a developer account to do so.
Method 2: You'll need to have an older version of the app backed up to restore it to that version.
Method 3: This method is not condoned by iPhoneForums since it is along the lines of piracy even though the Facebook app is free, and will not be discussed or further instructed and is for you to dwell on.