Etag/Last Modified - the numpty question I've always wanted to know.

[p83822]

So, using Google-speak, cache-control: max-age/s-maxage and expires headers are "strong caching headers" while etags and last-modified headers are "weak".

Google recommend only one of each kind - which make perfect sense, but they also recommend one weak and one strong.

2 question chaps - and I've only just plucked up the courage on this one as I'm sure I'm asking a bonehead question:

1. Which strong and which weak one do we choose? (Google recommend expires over cache-control: max-age, but they are vague on the reasons.)

2. Why do we need a weak cache header at all? The behaviour I think I get (but I'd love to know others' observations) is endless conditional GETs each of which gets a 304; where what I think I'd like is just a single new unconditional GET and then no traffic for as long as the strong header mandates.

Be gentle chaps

N