Use Thumbnail Galleries to Display Small Previews of Large Images.
Above thumbnail images are linked to full sized pictures. Click on
a thumbnail to open the full sized image in a new full sized browser
window. Thumbnail galleries are used in photo galleries, shopping
carts and anywhere detailed images are needed but, are too large
to display because of the excessive download time they require.

Use Thumbnail Galleries to Display Images in Resized Windows.
Above thumbnails are linked to images which open in resized
browser windows which do not cover the current window and
allow simultaneous viewing of images and the thumbnail gallery.