When I add JSF capabilities to my web project and select MyFaces 1.1.1, the changes to my web.xml file include:
<filter>
<filter-name>MyFacesExtensionsFilter</filter-name>
<filter-class>org.apache.myfaces.component.html.util.ExtensionsFilter</filter-class>
<init-param>
<param-name>maxFileSize</param-name>
<param-value>20m</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>MyFacesExtensionsFilter</filter-name>
<url-pattern>*.faces</url-pattern>
</filter-mapping>
That particular filter-class is deprecated.
Also, I would suggest mapping the filter to the Faces Servlet rather than to the URL pattern. This would allow me to change the URL pattern for JSF in just on place.
These changes (plus an additional filter mapping to /faces/myFacesExtensionResource/*) appear to be the suggested web.xml configuration from Apache: http://myfaces.apache.org/tomahawk/extensionsFilter.html