I just registered EP and my home site with Google Webmaster Tools, and discovered they offer a 404 (page not found) service for replacing your existing not-found page with Google links which should include useful suggestions from your site. At the moment I just get a search box with the non-existent page name pre-filled, which is still a useful improvement.

I had the default Apache 404, and it's fine but it's not particularly useful or friendly, so I set up the Google alternative. Somewhat to my surprise, Google doesn't offer Apache httpd instructions for actually creating the 404 page, so here's my 3-step recipe for httpd 2.2.

1) Create a new page.

Mine is /var/www/error/404-google.html, accessible directly at http://www.reppep.com/error/404-google.html.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
    <title>404: Page Not Found</title>
</head>
<body>

<script type="text/javascript">
  var GOOG_FIXURL_LANG = 'en';
  var GOOG_FIXURL_SITE = 'http://www.reppep.com/';
</script>
<script type="text/javascript" 
    src="http://linkhelp.clients.google.com/tbproxy/lh/wm/fixurl.js"></script>

</body>
</html>

2) Enable the Google 404 in httpd.conf.

ErrorDocument 404 /error/404-google.html

If you already have a custom 404 defined, disable it.

3) Reload the server configuration.

[root@inspector ~]# apachectl graceful