Custom Error page problem

[prabodhachyutha]

All,
I have placed 404,500,501 error codes in web.xml as shown below and
the url http://localhost/webdynpro/asjkldhjklasdfh displays a custom
error page (here temp_error.jsp) except in case of the url
http://localhost/webdynpro/dispatcher (dispatcher is servlet name and
the corresponding entries in web.xml are shown below)where it is
displaying a Page cannot be displayed ( i require a custom page to be
displayed instead of this).Please help me how to show a custom error
page instead of a page cannot be displayed

</error-page>
<error-page>
<error-code>501</error-code>
<location>/customerrors/temp_error.jsp</location>
</error-page>
<error-page>

<servlet>
<servlet-name>dispatcher</servlet-name>
<display-name>WebDynproDispatcherServlet</display-name>
<description>no description</description>
<servlet-
class>com.webdynpro.serverimpl.defaultimpl.DispatcherServlet</servlet-
class>
</servlet>
<servlet-mapping>
<servlet-name>dispatcher</servlet-name>
<url-pattern>/*</url-pattern>
</servlet-mapping>

Thanks in advance.