3
Custom error pages are part of your server configuration, but if you can create .htaccess files, you can specify your own error pages.
For example, just add -
ErrorDocument 404 /search.php
to get redirected to the search page whenever the page they requested is not found.
If you want to display the system redirect page first -
Add a new page in your XOOPS folder with
include "mainfile.php";
include "header.php";
redirect_header(XOOPS_URL."/",3,"your redirect message");
Then use your .htaccess to point at your new page. Test it and you should be good.