is generated dynamically on the server, but provided you have your own domain you should be able to display your own page. This is how you do it.
1. Look in the root directory of your site and see if there's a file called: .htaccess
2. If it's no there you'll need to create it, and you do this by opening Notepad and creating a blank file called : .htaccess
Note that the filename starts with a dot - this means that it isn't really a file at all, the suffix (filetype) is htaccess.
3. Now add this line to the file - type it all on one line:
ErrorDocument 404 click here name of your domain in full/name of your custom page.html
(Note that I have left spaces in the mock address to prevent the forum site from making it into a blue 'click here' link).
4. Create your custom page and upload it to the server.
5. Put your newly created .htaccess file into the root folder of the site (that's the folder that contains the homepage) and make absolutely sure that the path to the custom page is correctly typed into the file.
It may be necessary to perform a small techie-typr job on the server before this will work, and you may want to check to see if your web host will do this for you. If the site's on a UNIX server you should be OK - otherwise you'll need to ask for the file permission: chmod 644.htacess to be set.