That page is displayed from the browsercache, there's very little you can do about it.

There are some hacks that disable backbuttons and stuff but those are easily circumvented (and will just piss off your users).
Another option is to set some headers that cause the page to expire immediately (which should but doesn't always prevent caching).

Rest assured, if your users try to do anything with that page they should (if you coded your webapp correctly) get an error.