I'm trying to integrate a custom 404 page via

 case 'error':
                  //includes about page if requested
         		require( dirname(__FILE__).'/_error.php');
         		break;

in my _main.php

The page displays fine using /index.php?disp=error

My question is: can it , or can it not be triggered by the .htaccess in the root and if it can, how?

I have used

ErrorDocument 404 /index.php?disp=error

which simply gives me the message "Sorry, there is no post to display..." and

/skins/customskin/_error.php

which gives me the Server default 404 page

I'm having no success, which isn't new for me :)