On Mar 17, 2004, at 19:52, Timwi wrote:

it seems that Wikipedia's HTTP response contains this header:

Cache-Control: private, s-maxage=0, max-age=0, must-revalidate

If I understand this right, this means that the page must not be cached by the browser.

Nope. That means that if you come back to the page, the browser must _check if it's changed_.

The second request will include an "If-Modified-Since" header including the modification date specified when the page was first visited. Either the squid cache or the wiki itself will compare this date to its knowledge of the state of the wiki, and if the page has not changed, sends a "304 Not Modified" response and the browser will show its cached copy.

If and only if the page _has_ changed, then the squid sends the more recent locally cached version or the wiki parses, renders, and outputs a new version.

This is necessary to, for instance, see the new version of a page after you've edited it.

Has this header always been there? Or has it been added recently? If so, can it be removed again? :)

Been there for a long, long time.

The reason I'm bringing this up is that I've noticed that Firefox has suddenly started reloading all pages whenever I use the "Back" function. It didn't use to do that until today. Hence, I suppose the header wasn't there before.

Did you load Internet Explorer by mistake? It's known to have this misbehavior (re-requesting the page on back/forward button press as well as actual link navigation).

-- brion vibber (brion @ pobox.com)