User-Friendly 404 Error Messages
http://www.smackthemouse.com/20030517

Tverskov, Jesper
Smack the Mouse
2003

Abstract:

An error message should be designed to the website. A good error message could be conceived as so positive that the error is already forgotten or forgiven. The article is a guide to good error messages using the dreaded "404 – file not found" as example.