Graham Fawcett wrote:

> Note that IMS is totally separate in intent from the Expires cache
> directive; it's an active protocol, not a caching hint.

On second reading, that's incorrect: both If-Modified-Since and Expires lend
toward the same intent (cache correctness and reuse), but their semantics are
different. They're complementary mechanisms, one being an assertion of
correctness from the server, the other being a hint about the life expectancy
of a cacheable item. Ideally a StaticFile server should use both correctly to
improve cache performance along the request chain.

I didn't intend to pose as an authority on HTTP/1.1 -- that's RFC 2616's job,
not mine. ;-)

-- G