TO MAKE A SCREENSHOT, FIRST CHOOSE THE WEBPAGE YOU WISH TO CAPTURE. THEN...
...click on Prt Sc (Print Screen) SysRq
You now have copied an image onto your clipboard.
Unload this image by going to IrfanView, PaintShop Pro, Photoshop, Paint or any graphics editor.
is found on every computer: Start > Programs > Accessories > Paint
To make your copied screenshot appear in Paint, go to Edit > Paste
Now you can edit the image.
Image > Stretch/Skew to make it smaller by 50%, for example.
Check the width and height under Image > Attributes
Save the image into your website images folder when you're happy with the size.
Save it as a gif or jpg - NOT as a bmp
To take a detail from a picture, select it - usually with a rectangular tool - and go to Image > Crop. Then save it as a gif (or jpg) with a relevant name