I DO Exist!
After hearing the explanation, I rememner this from the 70's and 80's!
Programmers DO have a sense of humour, and in those days it was more freely expressed as computing was something of a closed shop among the "geek" community. Unfortunately, some of these curiosities have lasted well into the 21st century where computer users far outnumber those of us with any idea of how to program the damn things.
The technical variant of the error message "you don't exist....." would certainly have made more sense. Even though the user would have no idea what it meant, it would at least look like a genuine issue rather than the result of a hacker's mischief.
Unix has similarities with MS DOS, and the Apple MAC operating system, it is nothing at all like Windows, with it's more understandable, although irrelevant, error messages.
I doubt this will be changed, as it is so deeply embedded in the Apache server OS.
I have tried the link just now, and Ritz seems OK again, I notice though, that I am informed my browser has been redirected to their new site, but that still carries the same URL.