This is a discussion on How To Quickly Take screen shot of window in Mac OS X within the Mac OS X forums, part of the Tutorials category; Using the following way you don't have to open Grab.app to take screenshot of just one window. 1) Press "Command-shift-4" ...
And command shift 3 for the whole screen.
ooh nice... but i noticed that you dont need to press and hold space
no just press it, "now Press "Space bar" and press at the window you want to take screen shot of"