Unfortunately, you can't guarentee that at all; the Expires header is defined in the standard, and therefore, any proxy should follow it, but as with users and homegrown browsers, they don't have to. I know that in recent discussions on my isp's newsgroups on the possibly of installing a proxy, most proxies that are used at a large scale site are home grown and typically have had much trouble with 80% of the web sites out there that *don't* follow the standard.
Again, falling back on a sessionid and other tracer should help prevent problems from cached page use.
Dr. Michael K. Neylon - mneylon-pm@masemware.com
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"You've left the lens cap of your mind on again, Pinky" - The Brain
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You wrote that those homegrown proxies had trouble with websites because the websites don't follow the standard?
Are you sure you don't mean it the other way around, that the proxies have problems because they don't follow the standard?
Please elaborate!
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It's a combination of both. It is up to the proxy to determine that a page is past the Expires point, and thus when requested again, it needs to go out and retrieve it, but I could easily write a proxy that is blissfully ignorant of this aspect. On the other hand, there are web sites that use a non-standard method for attempting to expire web pages, and thus don't play well with proxies that do follow the standard.
Dr. Michael K. Neylon - mneylon-pm@masemware.com
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"You've left the lens cap of your mind on again, Pinky" - The Brain
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I want to prvent caching on all levels...
Remember, you can't prevent anything. This is the #1 thing
that web creators seem to be not able to understand: Once that
page leaves your server, it's outta your hands. You don't
know who's going to render it, or cache it, or index it, or
whatever.
Basically, my point is, the cache things are suggestions at
best. Nobody enforces them, and Lord only knows what mutant
and/or broken browsers might be out there.
xoxo,
Andy
# Andy Lester http://www.petdance.com AIM:petdance
%_=split';','.; Perl ;@;st a;m;ker;p;not;o;hac;t;her;y;ju';
print map $_{$_}, split //,
'andy@petdance.com'
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