404 - Page not Found

I'd just like to interject for a moment. What you're referring to as this "404 page" is in fact not a page at all, but rather a diagnostic message of a missing resource.

This resource is not present on this server. It has either been removed, renamed, or was never part of the site to begin with.

Many users attempt to access nonexistent pages every day, without realizing it. Through a peculiar turn of events, the URL which is widely used today points to nothing, and many of its users are not aware that it is basically invalid.

There really is a resource, and you may be trying to use it, but it is just a part of the site you intended to access. The path is the locator: the mechanism that allocates requests to the resources that actually exist.

A locator is an essential part of the Web, but useless by itself; it can only function in the context of a complete and correct URL.

All the so-called "broken pages" are really requests for resources that do not exist.