Re: HTTP/1.1 Issue: max-age in responses not defined

>>    The max-age directive on a response implies that the
>>    server believes it to be cachable.
>Does it mean that: if there is a max-age in a response, it is cacheable
>(independent of the value of max-age)?

Yes, but not independent of other parts of Cache-Control (like private).

>So, if a server wants a response to be treated as uncacheable then should
>it return a Expires = Date or max-age set to zero?

It should return Expires = Date and Cache-Control: no-cache
The first is for HTTP/1.0 caches and the second id for HTTP/1.1 caches.
Note that max-age=0 means "cachable, but treat as stale on future requests".

.....Roy