Good browser caches are our friend, it make users happy and it makes servers happy.

But sometime caches can be a nuisance. Right now this is the case for doing a Zimbra upgrade. Everything is in halfway states for most users, all kinds of strange behavior of mixed up 3.1 and 4.0 UI until their browsers cache is flushed. Not quite sure why but Zimbra seems a little more cache sticky than most webapps, I know theres even an extra parameter put in for version to try to work past this, but it doesn't seem to work most of the time.

Still it seems simple enough to just flush the cache. I mean in development I even have my cache turned off. But what does one do with a really large user base? Its really not practical to walk a thousand people through flushing the browser cache.

Is there anything that we can do programatically? Anyone have any advice on this?