Plain old static html error pages are in-descriptive and frustrating, one of the main to reasons webmasters commonly choose to make a mistake and redirect all 404s to their home page. Instead of redirecting, use PHP to let the user know what page they were trying to access and a note saying it no longer exists. Then give them a couple of options such as go back to referring site, continue your site's home page, etc.

You might also integrate an email function to let yourself know a page is no longer up, or a site is linking to a non-existent page on your website. Even an option for the visitor to report the non-existent page is a good idea.

Professional website developer at simplyPHP.com.