If you use windows, hit the print screen key on your keyboard. Then open an image program like photoshop or paint shop pro and make a new image (usually by pressing control-n). Then press control-v to paste your screen shot into the new image. Save the image as a jpg or gif file using the export or save for web feature of your image program.

On a mac, press control-shift-apple-4. Your cursor will turn into a little cross hairs. Select the area you want to capture with your mouse (you will hear a little camera noise). Then open photoshop, or fireworks or whatever, do a apple-n to make a new image. Then do an apple-v to paste the screen grab into the new image. Save as a jpg or gif using the export or save for web feature of your image program.