404 with no URL change in address bar?

[der100]

I have a site with a custom 404.php page where
http://domainname.com/directory -> 404.php if "directory"
doesn't exist.
Is there a way to make it so that http://domainname.com/directory
remains in the browser's address bar and not http://domainname.com/404.php ?

[tomws]

You're looking for the ErrorDocument (http://httpd.apache.org/docs/2.0/mod/core.html#errordocument) directive for your config.