Custom error pages are not working IIS 7.0- It’s display the default error page

We are having our site hosted on IIS 7.0 and Integrated mode and we have already set the custom error page like following.

  <customErrors defaultRedirect="Error.htm" mode="On">
        <error statusCode="404" redirect="Error.htm"/>
   </customErrors>

It is redirecting url from the error page like following but its not displaying the url http://www.example.com/Error.htm?aspxerrorpath=/and its showing following error:

Runtime Error

Description: An application error
occurred on the server. The current
custom error settings for this
application prevent the details of the
application error from being viewed
remotely (for security reasons). It
could, however, be viewed by browsers
running on the local server machine.

Details: To enable the details of this
specific error message to be viewable
on remote machines, please create a
tag within a
"web.config" configuration file
located in the root directory of the
current web application. This
tag should then have
its "mode" attribute set to "Off".

      <!-- Web.Config Configuration File -->
     <configuration>
     <system.web>
       <customErrors mode="Off"/>
     </system.web>
    </configuration>

Notes: The current error page you are
seeing can be replaced by a custom
error page by modifying the
"defaultRedirect" attribute of the
application's
configuration tag to point to a custom
error page URL.

           <!-- Web.Config Configuration File -->

           <configuration>
           <system.web>
              <customErrors mode="RemoteOnly"

defaultRedirect="mycustompage.htm"/>