On Monday, December 10, 2001, at 11:55 PM, Nathan Wheat wrote:
> I think the recommended HTTP headers are as follows:
>
> <% response.setHeader("pragma", "no-cache");
> response.setHeader("Cache-control", "no-cache, no-store,
> must-revalidate");
> response.setHeader("Expires", "01 Apr 1995 01:10:10 GMT"); %>
>
> That might cover it...! :)
>
Maybe, but here is an excerpt from the HTTP 1.1 spec (rfc 2616):
>
> 13.13 History Lists
>
> User agents often have history mechanisms, such as "Back" buttons and
> history lists, which can be used to redisplay an entity retrieved
> earlier in a session.
>
> History mechanisms and caches are different. In particular history
> mechanisms SHOULD NOT try to show a semantically transparent view of
> the current state of a resource. Rather, a history mechanism is meant
> to show exactly what the user saw at the time when the resource was
> retrieved.
>
> By default, an expiration time does not apply to history mechanisms.
> If the entity is still in storage, a history mechanism SHOULD display
> it even if the entity has expired, unless the user has specifically
> configured the agent to refresh expired history documents.
>
> This is not to be construed to prohibit the history mechanism from
> telling the user that a view might be stale.
>
> Note: if history list mechanisms unnecessarily prevent users from
> viewing stale resources, this will tend to force service authors
> to avoid using HTTP expiration controls and cache controls when
> they would otherwise like to. Service authors may consider it
> important that users not be presented with error messages or
> warning messages when they use navigation controls (such as BACK)
> to view previously fetched resources. Even though sometimes such
> resources ought not to cached, or ought to expire quickly, user
> interface considerations may force service authors to resort to
> other means of preventing caching (e.g. "once-only" URLs) in order
> not to suffer the effects of improperly functioning history
> mechanisms.
>
>
>
I take this to mean that cache control probably won't affect back
buttons at all.
ch
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