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.

Response.Expires and Response.CachePolicy are the things you want to look at for setting the expiration rules.

+++ Rick ---

>>I found this article: http://www.dotnetbips.com/articles/displayarticle.aspx?id=288
>
>The issue is not to force a read from the server at every hit but to make sure the user gets a page has expired when he goes back. To my knowledge so far, this is something that cannot be done. Basically, the client requests that the back button would return an empty page or something like that because they do not want to user to hit on a link from a previous page. The only think I have found so far in this Web thing is when the page has been posted. But, to have a general way of doing this is not possible.