Alt-PrintScrn captures an image of the currently active window in the Windows clipboard, and you can then paste (control-V) the image into another program fand then save the image as a .BMP, .GIF, .JPG or other type of graphics file.

For HTML documents, you'll want to save the image as either .GIF or .JPG. Typically, you should use .JPG for photos (which have lots of different colors), and .GIF for images such as cartoons tha have fewer distinct colors.

You can download an image-handling program, Paint Shop Pro, for free. Paint Shop Pro has two wonderful features in its menus: (File...Export...GIF Optimizer) and (File...Export...JPEG Optimizer). These wizards help you save any graphic by compressing the file down to a point where the size is small but the image still looks good. PSP also has good resizing and other features. The commercial version costs ~$100.

The full procedure to capture a screen shot thus is:

1. Open the Window you want to capture
2. While that Window is active, press Alt-PrintScrn
3. Open Paint Shop Pro (or another graphics program) and paste the captured image into the program by entering Control-V.
4. Save the image as a .JPG or .GIF file using the image export optimizer (or an equivalent function in another program besides PSP).
5. Use the image in your web page.