Capture screenshots correctly on android.

Screenshots are often used for documentation. In case of android devices, taking screenshots is bit tricky and steps vary as per the android version.
In versions before android 4
Screenshot can be captured by keeping the home + volume decrease buttons pressed for few seconds.
From android 4 to version 4.0.3
You'll need to press the POWER button + Volume decrease button together for few seconds.
From android 4.0.4
Screenshot can be captured by pressing home + volume decrease buttons for few seconds.