Jeanne,
You can change the mapping inside the "web.xml" file for your Web application. Notice below that I changed the mapping to "*.xyz".
<!-- Faces
Servlet -->
<servlet>
<servlet-name>Faces Servlet</servlet-name>
<servlet-class>javax.faces.webapp.FacesServlet</servlet-class>
<load-on-startup> 1 </load-on-startup>
</servlet>
<!-- Faces Servlet Mapping -->
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xyz</url-pattern>
</servlet-mapping>
Hope that helps,
-James
JSF Resources and Faces GUI tool
http://www.jamesholmes.com/JavaServerFaces/