If you want to add Lightbox to a Magento Install, begin with the following instructions (  http://www.magentocommerce.com/wiki/adding_lightbox_to_magento_v2 ).

I was using the modern theme and had to modify the instructions as follows:

Go to /js/

Create a directory: /lightbox

and copy the lightbox.js file to this directory

The “/js/” directory is the top most “JS”directory of the magento install. It did not work if you put the lightbox.js file in the /skin/frontend/default/default/js/ or /skin/frontend/{your}/{path}/js/lightbox