You would have thought that including one page in another was a simple thing to do. You would be greatly mistaken if you held this notion for JSF. A number of querks with the way JSF is integrated with JSP make includes supprisingly difficult. Actually that's not strictly true. Includes are quite easy as long as you only want to include verbatim HTML with no JSF tags which I think is fairly unlikely.
An example of a very simple include is shown below using the index.jspx and simple_header.jspx files. Note that the included page has to be a f:subview of the main view or it will fail. In this case the index page is a JSF page itself and is processed with the FacesServlet alread so you don't include the header as a JSF (eg using .jsf as the file extension) since that would attempt to run the included page separatly through the FacesServlet which causes an IOException because the output stream has already been closed.
The File "index.jspx"
<jsp:root version="2.0"
xmlns:jsp="http://java.sun.com/JSP/Page"
xmlns:c="http://java.sun.com/jsp/jstl/core"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html">
<jsp:directive.page contentType="text/html"/>
<f:view>
<f:loadBundle basename="localization.messages" var="text"/>
<f:verbatim>
<![CDATA[<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3c.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">]]>
</f:verbatim>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Example</title>
</head>
<body>
<jsp:include page="simple_header.jspx"/>
</body>
</html>
</f:view>
</jsp:root>
The File "simple_header.jspx"
<jsp:root version="2.0"
xmlns:jsp="http://java.sun.com/JSP/Page"
xmlns:c="http://java.sun.com/jsp/jstl/core"
xmlns:f="http://java.sun.com/jsf/core"
xmlns:h="http://java.sun.com/jsf/html">
<f:subview id="header">
<f:verbatim>
<p>Bar</p>
</f:verbatim>
</f:subview>
</jsp:root>