Even if your Web site is rock-solid with no broken links on it anywhere, chances are someone is going to see a 404 File not Found error page someday, if only because the user typed in an address incorrectly. For that reason, it’s a good idea to customize it–the default 404 page is distinctly unhelpful. A good 404 page should inform the user that the page wasn’t found, and provide links to the front page of the site, the search page, the index, or wherever. It should also use a meta-refresh tag to automatically send the user to the front page of the site after some interval–10 seconds is a good first guess.
For Apache and Netscape Web servers, the place you specify your 404 page is in the srm.conf file, on the line that contains:
Uncomment it if it’s commented out, and give it a path to the custom error page you’ve created.