Our new function cpg_error is called when an error (regular and database) occurs, displaying the error and it's details.
When a query to the cms_config_custom or cms_users table fails or when a connection to the database fails or is closed, the system wouldn't know what theme to use for the error page. This is why the error pages cannot be theme-based.
We could have handled such pages with just a white page with some text but that's not cool. So we designed cpg_page.php.
The file is located in the includes folder on your server. Two functions exist in this file: cpg_header() and cpg_footer() which are both called by cpg_error().
We use this for handling various HTTP errors, and is activated through .htaccess.
You can easily change this file any way you like.
Bear in mind that, if you activate the email notification, in exceptional circumstances your host may not appreciate a large volume of emails being sent.