The multi-tasking feature released with iOS 4.0 is a great feature to allow you to run more than one application at one time; however, the implementation assumes you always want to keep each app running (in a minimized fashion) rather than closing them – so, with iOS 4.0 instead of closing the app when you click the home button, it simply allows the app to run in the background.  To see what apps you have running, press the home button twice.  This will bring up the multi-task bar which shows all the apps running in the background.

To close an application that is running in the background, follow these steps:

  1. Push the home button twice.
  2. Push and hold down one of the app icons showing in the multi-task bar - this will cause the app icons to jiggle (similar to when you re-arrange apps on the main screens) & have a red circle with a minus sign.
  3. Push the minus sign to close the application.

You may want to close applications you don’t want running in the background for the following reasons: [more]

  1. Memory – each application running is taking up memory
  2. Security – applications may be running services in the background that you don’t want running
  3. Battery – having multiple applications running in the background will drain your battery quicker