Custom error page
You can customize the content and the look-and-feel of the default page that is displayed on your web server when a 404 File Not Found error occurs. A good 404 error page has a friendly message explaining that the page they requested doesn't exist at the location, a site map to encourage the user to continue exploring the site, a search box so the user can conduct a search, and a look-and-feel that matches the rest of the site, including navigation of course. Creating a custom 404 error page not only helps keep visitors in your site, it is also an important part of the search engine optimization process. Inevitably pages on your site will get moved and removed over time. When a search engine spider returns to your site to reindex those now non-existent pages, they will have a set of links to explore in the form of the site map on the custom 404 page. You can test for whether a site has a custom 404 error page by trying to access a web page with a nonsense filename after the domain name in the web site address. For example: www.yourcompany.com/blah
