logout problem

 Hi
I've an ecommerce site and not all of it's pages require authentication. And I am using custom login and logout controls not asp.net 2.0 own.
The problem is that as to many novices, when the logout button is clicked, users logged out and redirected to the logout page.
ok
but when the back button is clicked the secure page is reloaded. I have used the following code
 
FormsAuthentication.SignOut();
Response.Cache.SetExpires(DateTime.UtcNow.AddMinutes(-1));
Response.Cache.SetCacheability(HttpCacheability.NoCache);
Response.Cache.SetCacheability(HttpCacheability.Private);
Response.Cache.SetNoStore();Session.Abandon();
Response.Redirect("Logout.aspx"); But the problem is still there. Also I don't want to use Javascript to disable back button. Also I am using Master pages.
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