Re: cache-proof servers?

> I have a setting for my Apache (sorry, no experience with other servers)
> that controls wheather the server's served docs are cachable or not, I
> suppose it's a header thingy you can enable to tell the cache server NOT
> to cache certain pages, like when the same URL produces random pages, or
> random ads (on commercial sites like Geocities and others, an
> advertisement chages on each reaload)

The best thing to to on "random" URLs is to make them return a
temporary redirect (http code 302). This will not be cached by any
cache server, but it permits the actual objects to be cached.
(the different objects of-course has to be stored on different
URLs)

If you have a object that changes on each request (like a counter),
then Expires: should be set to the same as Date: to prevent it
from being cached (immediately expired).

And if you know that a object will be updated at a certain time (for
example on Mondays), then Expires: should be set to this time...

If you don't know when the object is going to be updated, then
you should at least send Last-Modified: to give a hint on how
frequently the object is changed.

And at all times, the server should send at least either Expires: or
Last-Modified: to give a hint on how long the object may be cached
(or not). The main problem is that most servers do not support
setting the Expires: header in a nice way (or at all). Some implement
this by using a HTML meta tag, but a more general method is needed
in order to set Expires: on other file types.

---
Henrik Nordström