how do I prevent client caching?

John Studarus (studarus+@CMU.EDU)
Sat, 22 Oct 1994 23:54:41 -0400 (EDT)

How do I tell a client to reload a page rather than
using the page in cache? I have some scripts that I
want clients to rerun rather than fetching stale data
from the cache. I don't want the client to click 'reload'
because the links don't always both to themselves but
to other scripts that have already been called and cached.
This problem occurs with the Mac and PC
versions of Mosaic.
I've appended nph- to the beginning of the
script name (I'm using NCSA httpd v1.3) and have my
scripts return the following headers:

HTTP/1.0 200 OK
Date: Sun Oct 23 03:49:03 UTC 1994
Server: my_server/1.0
Expires: Sun Oct 23 03:49:03 UTC 1994
Message-id: 782884143a
MIME-version: 1.0
Content-type: text/html

rest of output deleted

Basically I'm setting the Expires date equal to
the creation date. But MacMosaic and MacWeb continue
to retrieve the file from cache! Mosaic for X works just
fine though, both before and after I started sending the Expires
info. I added a unique Message-id as well but that didn't
do any good.
What's the secret??? =)
Thanks,

-John
studarus@cmu.edu

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