I just read RFC 1738 ( http://gim.org.pl/rfcs/rfc1738.html ):
For resiliency, programs interpreting URLs should treat upper case letters as equivalent to lower case in scheme names
So I tried to visit http://gim.org.pl/rfcs/RFC1738.html instead of http://gim.org.pl/rfcs/rfc1738.html. I received 404.