Are the links on your web site all functional? Probably not. The rate at which sites come and go together with a couple of broken HREFs within your pages means that someone will sooner or later get a file not found (unless your pages are on servers such as Geocities that send out their own page when an inexistant page is selected). This is one of the checks you can make at NetMechanic.

Here is a complete list:

GIFBot: Reduce the size of your Web graphics by up to 90%.

Link Check: Check your site for dead links.

Server Check: Test your Web site.

HTML Check: Check bad HTML tags and syntax.