The key to a good SEO plan is to never create a web site for the search engines, but rather create one for your users and the rest will fall into place. There are many examples of this practice, but perhaps one of the most obvious is The 404 - File Not Found – page, which is displayed to users as an error page when a file does not exist on the server. The server automatically generates these generic 404 error pages when a user enters an invalid URL, on a domain that does exist.

Search Engines don’t like seeing this and would much rather see a customized web page with content and a few links, such as a link back to the previous page, home page and site map. However, this error page is even more annoying to the user of the web site. They don’t want to see an error, but rather they want to be told the page does not exist, and possible links to pages they may have meant to visit. In many cases a free text search is a great tool to provide users to locate a page with the content they are looking for. It also helps a user to see a familiar design, in that, the GUI the user has been viewing all along creates the appearance that the web developer was thinking of the user when they cratered the customized 404.
Many hosting companies offer a 404 redirect page. This can usually be set easily in the control panel, under some link such as error messages, or HTTP headers.

One of the more common practices is to just add a 302 or 301 redirect to any URL that does not exist, and send the user back to the home page. However, the problem with this is that the user may think they are stuck in a loop and keep trying to get to a page that does not exist. They may even think that there is a programming problem and leave your web site. It is a much better idea to show the user a unique page which tells them the page they entered is not available any longer.

Some things you may want to put in your page can not be found 404 Error page are:

1. A statement of apology for the page not being found;
   
2. Provide links to the home page, sitemap, and contact page;
   
3. Offer assistance and encourage the user to continue to search for the information he needs on your site. You could even include a search box right on the error page;
   
4. Put all the content with in your standard GUI.