In the Web.Config for your Live web site, to prevent Server Application Error messages being displayed to your customers, set the CUSTOM ERROR MESSAGES to the following settings:
<customErrors defaultRedirect="~/SiteMessage.aspx" mode="RemoteOnly"/>
In the event of an error on the web site, a 'friendly' message is displayed to the user and a Web Error email message is sent to the web site administrator. No emails are sent unless the CUSTOM ERROR MESSAGES is set properly.