In the early days, most Android phones could only capture what was on-screen using extra tools or apps, most of which required root access first. The Samsung Galaxy S2 has a built-in screen capture utility, so taking screenshot is easy and doesn't need rooting or installation of third-party apps.
The Samsung Galaxy S2 screenshot app is invoked when you press and hold the HOME button then press the POWER button. You get the camera shutter sound and a flicker on the screen as the utility grabs what's displayed. It works flawlessly every time, with the image saved to the phone storage, in a screencapture folder. This is for Android 2.3.
For the Android 2.4 'Ice Cream Sandwich' version just released, the same utility for taking screenshots on Galaxy S2 or S3 runs but the controls are changed to Volume Down and Power Buttons: press and hold the VOLUME DOWN and POWER buttons simultaneously to take a screenshots. RC