This doesn't seem to be explicitly spelled out one way or the other in
the HTTP/1.0 spec, but the mailcap spec makes it pretty explicit --
"If the subtype is specified as "*", it is intended to match all
subtypes of the named content-type."
I'd strongly encourage adoption of this methodology by HTTP/1.0 and
the servers, as it makes the user's life much easier and it makes it
possible for browsers to conform to RFC 1343.