well, this is what i've done.
create a file named: .htaccess and put it in your webroot directory.
inside of it put this line:
ErrorDocument 404 /404handler.php
// or ErrorDocument 404 /directory/error/404handler.php
save the file and it should work.
now if you have access to the apache setup file httpd.conf
you have to add that line above, somewhere in that file. You'd have to look into the file itself and or apache docs to find where to make those changes exactly.
hope this helps.
