If you're a PC user, you might not be used to Apple's habit of making one button do many things. And even though technically the iPhone has four buttons, if you include the volume controls, pretty much all the resetting, rebooting, and reprogramming of the iPhone uses just two buttons—Home and Power.
The first hack of note is Force Quit. This is the equivalent of Command-Option-Esc/Force Quit on a Mac, or Ctrl-Alt-Del/End Process on a Windows PC. If you're in an application on the iPhone that is hung or isn't responding quickly enough because of network access or some other problem, you can get out to the Home screen.
To force quit an application that's frozen, press and hold the Home button for at least 6 seconds to close the frozen application
There are other applications that capture this button push and may make it do something different. For instance, if you're using Lance Fetter's backgrounder application, you might see a "Backgrounding Enabled" message. In this case, just continue to hold the button and the app will quit.
If your iPhone is still sluggish or unresponsive after you force quit the application, the next thing to try is rebooting.
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