What suggestions should I consider when creating a custom 404 File Not Found error page?

When a visitor encounters a 404 File Not Found error page on your site, the visitor, whom you've worked hard to obtain through the search engines or third party links, is on the verge of being lost. Creating a custom 404 error page helps you to minimize the number of visitors lost in this manner.

Your 404 error page is accessible via FTP here:
custompages/errors/404.htm

Here are some tips to help you:

• Include a link to your main page, with a suggestion that the visitor can find what he wants there.
  
  
• Include a link to your sitemap, which lists all the pages on your website.
  
  
• Some users include a list of frequently mistyped URLs with a link to the correct URL. If you are aware of frequently mistyped URLs, you should consider ordering 301 URL Redirect Service.
  
  
• Consider making your 404 page larger than 512 bytes; otherwise, Internet Explorer (IE) may load what it calls its built-in "friendly HTTP error message" instead of your 404.htm page.

Avoid these mistakes when creating a custom 404.htm page:

• Ensure your custom 404 error page is sending a 404 header. If you load a file that doesn't exist, the http header should read 404 Not Found, NOT 200 OK. If your custom 404.htm file does not return the correct header, the 404.htm file will have to be removed until it is corrected.
  
  
• Use 301 redirects instead of a 404 error page when possible. 301 redirects are user and spider friendly; the 404 error page is not.
  
  
• Don't forget that your 404 error page may be loaded either from the main directory or from a subdirectory and in either http:// or https:// (secure) modes. You should use absolute paths when creating links and use protocol-relative image src paths for images.
  
  Example:
  use: <img src="//<PrimaryURL>/images/logo.gif">
  instead of: <img src="images/logo.gif"> or <img src="http://<PrimaryURL>/images/logo.gif">