"Four - oh - four" errors are probably the most common errors people encounter on the web. There are a number of reasons why they occur. Here are some of the most common:

• You typed the wrong URL (webpage address).
• There is an error in the page you were just at. The link you followed leads to a page that no longer exists.
• The page you just came from is under construction and not all the links work quite yet

Except for the first problem, these are all problems which the average person browsing can do nothing about. In order to fix these errors, you have to be the author.

For Authors:

Authors should always check the links on their site to make sure they work before publishing their work. Capitalization does matter. http://www.sju.edu/infotech/ is not the same as http://www.sju.edu/INFOTECH/ or http://www.sju.edu/InfoTech/. Only the first one is a valid URL.

So watch your HTML!