Something bad happened. But we still love you
Sorry the page you are looking for doesn't exist or something is not working
When you have used the web for some time, you know that an URL does not always lead
you to what you expected and that links can be broken. Just like telephone numbers.
No big deal. You don't need to hear "we are sorry", or to be presented for a long
list of possible causes or a similar long list of suggestions for how to proceed.
We want to recognize that a "404 Not Found" has happened as fast as possible. It is not necessarily better to make a less technical message.