The problem you faced with may be solved in web.xml file stored in the WEB-INF dir in your web application project. You need to open that file and add the following xml content in order to make your pages running properly.
<web-app>
...
...
...
<servlet-mapping>
<servlet-name>Faces Servlet</servlet-name>
<url-pattern>*.xhtml</url-pattern>
</servlet-mapping>
</web-app>
If your .xml file doesnt exist in the mentioned dir, you can add it by clicking on your web application project, add new file and then choose Standard Deployment Descriptor (web.xml)