PHP & Error Pages
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.