Hi David,
All dynamic pages, are "not cached" by default.
Static pages with the first line
<!-- NetWebServer -->
are considered to be dynamic.
there is also a property you can set in the WebHandler, say in the ProcessLink method (before the parent call)
self.ForceNoCache = 1
Regarding the browser back button - that's a lot tricker as it's essentially up to the browser as to how they handle that. ie it's a "browser thing" not a "server thing". However if your site is secure, and the pages are not cached, then you should be ok.
You'll notice on banks that they also encourage people to explicitly "log off" before leaving, and explicitly close the browser before leaving - these are both good behaviors as a user when using secure sites..
Cheers
Bruce