(offtopic, but related...) is "http://%77ww.apache.org/"; a valid URL refering to the same resource that "http://www.apache.org/"; does?
RFC 2616 section 3.2.3 seems to imply that, for comparison purposes, they are the same. RFC 2396 on generic URIs defines "server" in a way that doesn't allow URI encoding, but that isn't specific to the http scheme, so it could be overridden. If a %-encoded hostname is valid in a URL, is it valid in a Host: header? And, from the practical side, is there any reason to allow %-encoded hostnames in URLs?
