I am a new Acer A500 Iconia tablet user and I am having difficulties trying to figure out how to go "back" or exit a screen when I am reading an EW magazine that I downloaded. There is no button for me to use in order to return to my desktop. I found the same problem occurs when I am playing some games or listening to the mp3 program. The only way I can get out of these screens is to shut down the device altogether. Any suggestions?