iPhone Quick Tip #2
If you have ever had an app lock up or freeze on you and refuse to close, you know what a pain it can be to regain access to your springboard. A full reboot is usually required...unless you know how to terminate a frozen app.
To terminate or close an app that has frozen or locked up your iDevice, simply press and hold the power button (top of iDevice) until the slide to power off screen appears. Once the slide to power off screen appears, press and hold the home button. This will terminate the currently running app, returning you to your springboard.
In addition to closing apps that have simply frozen, it is sometimes a good idea to close an app using this method. By closing an app this way, you can rest assured knowing that background processes are being terminated as well. This will increase battery life and available memory!
Apps such as Safari, iPod, and Mail often refuse to close down completely on their own without following this process.
If this method fails to close your frozen application, your iDevice is completely locked up. You can do a hard reboot; See Quick Tip #3 for more details.