Ask PG: Why when I go to /CLASSIC does it show "Unknown"?

I had my caps lock on today and went to http://news.ycombinator.com/CLASSIC instead of http://news.ycombinator.com/classic and all I got was a white page saying "Unknown." I just checked and this happens with several urls (http://news.ycombinator.com/LEADERS, for example).

I'm a Windows guy and IIS (the Windows built-in web server) isn't case sensitive. I also don't care to search around and figure out what web server you are using (apache?). So the question is: is this by design or accident? And if it's by design, why?

And BTW - I don't care one whit if you fix it or don't; it doesn't affect my usability at all. I was just curious.