I know 2 ways:
1. Working with Web Config(
recomenved). U just need to set below code in Web.Config file.
Code:
<customErrors defaultRedirect="urErrorPage" mode="On|Off|RemoteOnly">
<error statusCode="statuscode" redirect="urErrorPage"/>
</customErrors>
2. Working manually on pages. Set below code on first line.
Code:
<%@ Page ErrorPage="errorpage.aspx" %>
HTH.
Always:),
Hovik Melkomian.