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I have had them clear out cache (in both FF and IE) as well as restart their machines. No one seems to have an issue looking at the changes from their home computers. Does anyone have any idea what could be causing the issue?
Use the "Live HTTP Headers" for Firefox/Mozilla to view the server response to request for one of these "non-updating" pages. If you don't see a Cache-Control header indicating that the page must be revalidated, then that's the likely cause -- *If* there is a cache in the network.
Ideally, you want your server configured to send the Cache-Control, Last-Modified, Expires, and Etag headers, with max-age defined in the Cache-Control header in addition to the caching policy.
Cache-Control: private, must-revalidate, max-age=2400
Expires: Wed, 16 Dec 2009 17:04:50 GMT
Last-Modified: Wed, 16 Dec 2009 13:34:24 GMT
The caching policy used in the Cache-Control header can and should vary according to the type of resource is being served. Servers can generally be configured to send different cache-policy headers depending on the MIME-type of the requested file, its URL or filesystem location, or combinations of these. HTML pages and resources that are updated as part of the work process should have short expiry times and be marked as "must-revalidate" -- and in some cases should be completely non-cacheable. Other objects such as images and media files may be cacheable over several days or even several weeks (beyond that, the advantages of caching reach a point of diminishing returns.)
There are some fairly good resources on-line for researching this. Try searching for "caching tutorial for Webmasters" and related phrases. But be careful; Some of the Cache-Control header attributes have non-intuitive behavior, and it's important to realize that if you set a very-long caching time on a resource, then once that resource has been cached by a client, you'll have to wait for that time to expire or notify the user to flush his cache before that user will ever see an updated resource. That is, the caching policy is fetched with the resource content today, and that content and its caching policy won't be re-fetched until it expires next week, or next month... You've told that client, "Here it is, don't come back for a month." So keep your cache-times fairly low until you are really comfortable with this whole concept.
Gee, I sure hope you've got a caching proxy in that network. Otherwise this post is kinda long!
Also below for the same page (second section before the separator line):
Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0