Ah, no, I see. You used both, the jQuery and prototype libraries in one document. Since they are two different frameworks that do have similar function names, however, they are incompatible, and that’s why it wasn’t working. You should decide for one
library (prototype, jQuery, or whatever else) and stick with it. And then you look for plugins/extensions for that one library. Since jQuery is the most popular JS framework, there are plugins for virtually everything, there are even multiple lightbox type plugins. So remove the lightbox you have right now and use one for jQuery. I can recommend fancybox
. And remember: If you have included the core library file already you don’t need the jQuery file tha might be provided with the plugin.