I can't answer all of these, but...
On 10 Dec 2000, Louis Theran wrote:
>
> Has anybody done a survey of how common HTTP clients generate
> conditional GET requests? (A quick search didn't turn up anything
> interesting.)
>
> I'm mostly interested in:
>
> * Whether If-None-Match is used at all
I don't know. You might be able to find statistics about the use of this
header on the W3C's web characterisation pages.
>
> * Whether Last-Modified timestamps are really being used as nonces
Most, if not all, modern browsers will only send if-modified-since headers
with exacly the same date as was in the last-modified header of the
response they try to revalidate.
>
> * Whether ``Cache-Control: max-age=...'' is respected
All HTTP/1.1 implementations should, and I believe that by now most of the
browsers and proxy caches out there implement HTTP/1.1.
Koen.
