This is a remote java script test page. This page has an image that rolls over. You need to have a javascript capable browser to get this stuff to work. This is a typical page from dreamweaver with a mouseover.
Notice that if you view the source of this page, between the HEAD tags there is quite a bit of unsightly coding in there. This causes big problems for search engine spiders as they have trouble trying to sort out javascript coding. Spiders will see this gibberish and ignore it completely.
One way however to try and help your page out with regard to being indexed, you can use a technique called remote javascript files. Basically you put the script into a plain text file and then reference it from your page. Click here for an example of the remote javascript in action.