[M.C.]

Ahh.. Ok, sorry...

May be is better to edit template and add redirector?

So I use same hack I mention.

Now edit template:
STANDARD_ERROR

find:

{vb:raw headinclude}

replace:

<vb:if condition="$show['permission_error'] OR $show['inlinemod_form']">{vb:raw headinclude}<vb:else />
	<!-- redirect -->
	<script type="text/javascript">
	<!--
	location.replace("http://path_to_your_error_page/forum/404.php"); -->
	</script>
	<noscript>
	<meta http-equiv="refresh" content="0; url=http://path_to_your_error_page/forum/404.php">
	</noscript>
	<!-- redirect -->
	</vb:if>