>This is browser specific. I can't remember the details now, but Internet Explorer always allows you to go back unless the last page was a post and you expired it. GET pages will always be accessible with Back button.
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>Response.Expires and Response.CachePolicy are the things you want to look at for setting the expiration rules.

Thanks, this confirms what I have found so far. In overall, there is no universal way of making sure that, no matter if this is a get or a post, the back button will face a page expired message.