If you want to add thumbnails of larger images on your page, and allow people to view the bigger version of it on the same page, you can use this simply, handy script to do it. When the browser clicks on the image, the image becomes it's originl size, and returns to it's thumbnail size on double clicking.

Simply copy that script into your < body > tag, where you want your thumbnail to appear. Remember to edit the height and width so the image appears in the right size!