Custom Error Page in asp.net

<configuration> 
  <system.web>
    <customErrors mode="remoteonly" 
                  defaultRedirect="DefaultError.htm">
      <error statusCode="404" 
             redirect="CustomMessage.htm"/>
      <error statusCode="403" 
             redirect="No_Access_Allowed.htm"/>
    </customErrors> 
  </system.web>
</configuration>