Você pode modificar o web.config.xml até mesmo para criar páginas de erro personalizadas.
<!-- CUSTOM ERROR MESSAGES
Set customErrors mode="On" or "RemoteOnly" to enable custom error messages, "Off" to disable.
Add <error> tags for each of the errors you want to handle.
"On" Always display custom (friendly) messages.
"Off" Always display detailed ASP.NET error information.
"RemoteOnly" Display custom (friendly) messages only to users not running
on the local Web server. This setting is recommended for security purposes, so
that you do not display application detail information to remote clients.
-->
<customErrors mode="RemoteOnly"/>
Referência: link