Every once and a while an iPhone app will freeze and you will need to quit the app.  While you can always retart the iPhone, just stoppping the frozen iPhone app is much easier.  Here’s how you do it:

Step-By-Step: Force Quit a Frozen iPhone Application

1. With the frozen app on the screen, press and hold the off button on the top of the iPhone as if you were going to shut off the iPhone.  The “slide to turn off” slider should appear.

2. Once you see the slider, then press and hold down the home button on the phone until the main home screen reappears.

That’s it!