Question: According to the Netbeans site (http://netbeans.org/features/javascript/index.html), Netbeans can be used for "Developing with HTML, JavaScript, and CSS". However, the IDE does not ship with a project type just for this. Instead, there is a project type for PHP or (if you have a release before 7.0), Ruby etc.
However, I just want to create a rich web application with Javascript/HTML/CSS. Perhaps there is a plugin for such a project type?

Answer: 
You can just create a PHP project and then not create any PHP code. You will need the PHP plugin installed first.

Source: <http://forums.netbeans.org/post-32661.html>
If your still looking you could try this plugin:
<http://weblogs.java.net/blog/timboudreau/archive/2006/08/netbeans_module.html>