problem is probably in Servlet mapping, what servlet container / app server you are using?
Does it support Servlets 3.0 API?
Have you defined Servlet mappings for FacesServlet in web.xml?
I guess I forgot to mention, I am using Glassfish 3.1.1 so I don't see a problem there. I have had no problems getitng the Prime Faces that are built into Netbeans working, or running regular JSF pages.
As I say, the only thing that doesn't work is the CSS, the functionality of the page appears to work, clicking on the button causes the popup to display and I get no compilation or runtime errors, except for page not found on the CSS