If Facebook has frozen on your iPhone, it's likely that you were multitasking or trying to upload photographs. Freezing typically happens when the iPhone's memory is overloaded. Fortunately, this is generally an easy problem to solve.
The iPhone tends to freeze when its memory is overloaded, or it is doing too many things at one time. If you are on Facebook, you might be multitasking on a few other apps at the same time, or you might be trying to upload a large media file, such as a photo or a video. This can all cause your iPhone to overfill its memory -- like a computer that runs too many programs at once. To prevent future freezing, minimise the number of programs you use at one time, especially when you're uploading media.
If you do not have the latest updates for iTunes, the iPhone's internal operating system and the Facebook application, you may experience glitches that cause your phone to freeze. Updates for these programs fix compatibility problems and known malfunctions, so it is important to check for updates regularly. To update your Facebook app, open the App Store on your iPhone and tap "Updates" in the lower-right corner. To update your iPhone, connect it to your computer, open iTunes, click its name under "Devices" on the left and click "Check for Updates" in the centre screen.
When your iPhone freezes, you should first let it sit for a few seconds. Sometimes, it will begin working again without any additional fixes. Don't tap the screen or the Home button repeatedly. If it doesn't start working on its own, hold down the Sleep/Wake button on the top of the phone for 10 seconds. A red slider that says "Power Off" should appear. Slide the button to power the phone off. Leave the phone off for 30 seconds; then turn it back on.
Reset And Restore
If you cannot power off the phone, press and hold the Sleep/Wake and Home buttons simultaneously for 10 seconds. The Apple logo should appear. This resets the phone -- sort of like a restart for a computer. Usually, a reset will fix any freezing problem. If, however, you cannot reset the phone or still have a problem, you will need to plug the phone into your computer to restore it. Open iTunes, click your iPhone's name under "Devices" on the left, and click "Restore" in the centre screen. This will revert your phone to factory settings, so only use this as a last resort.