This tutorial shows you how to create a custom 404 error page within your Mambo or Joomla 1.0 web site and set it up as the default 404 page for your web site. Using the methods described here you can not only create a useful 404 page for your site visitors but it will also send the correct headers.

My guide to .htaccess has been very popular on both the Mambo and Joomla! forums. Due to popular demand, I am reprinting it here for you.
.htaccess files are "distributed configuration files" and provide a way to make configuration changes on a per-directory basis. What you can put in .htaccess files is determined by the AllowOverride [...]

What You Need to Run The Mambo Open Source Content Management System
The minimum system requirements for running Mambo on your server space are:
Apache
The operating system Apache is installed on can be anything that the Apache platform supports, but it is Linux, Mac OS X, Windows 2000/XP and BSD that has been tested properly with Mambo. [...]