When using MyFaces or Facelets you have to turn off the exception mechanism of them to use this demo.
See in the MyFaces Wiki:
Handling Server Errors
An exception is thrown in the application. The servlet container forwards to a page defined in the web.xml.
The navigation handler refers to a non existing page. The error code 404 in the web.xml is affected.
The navigation handler refers to a page with a syntax error.