if you're using expires, then you're doing the right thing... but if the page still shows up when you click back, this is the fault of your ISP probably having a cache that doesn't respect HTML headers..

and what's with the refresh?? of course you'll see the page when you refresh it.. or do you want everyone to view it only once in their lifetime??

Maybe the problem is with your code, that's how it should be:

print $query->header(-type=>'text/html',
                             -expires=>'-1d');
[download]

Update: Re-read it, the expires is in the header not in the starthtml