<customErrors mode="On" redirectMode="ResponseRedirect" defaultRedirect="~/Error/">
  <error statusCode="404" redirect="~/Error?errormsg=404_Not_Found"/>
  <error statusCode="500" redirect="~/Error?errormsg=500_Internal_Server_Error"/>
</customErrors>

routes.MapPageRoute("ErrorRoute", "Error", "~/Errorpage.aspx");

routes.MapPageRoute("ProfileRoute", "Profile/MyProfile", "~/Profile/MyProfile.aspx");