Expires: header with session

For some reason, whenever there is a session variable, the Expires: header on form results is set to Thu, 19 Nov 1981 08:52:00 GMT, even if I try to override it by sending my own Expires: header set to some reasonable time in the future. This is very annoying for Win-Netscape-4 users, who are then unable to use their "back" buttons after submitting a form. Likewise it seems impossible to View Source using Netscape after submitting a form. I can understand making this the default behavior (since many programs that receive forms are not equipped to deal gracefully with multiple submissions of the same data), but making it unavoidable creates some problems. Or perhaps I'm missing something? With IE I was able to get around it by sending this header: Cache-Control: private, max-age=10800 Barring a straightforward remedy within PHP, is there something similar which will get Netscape to cache form results? miguel