Warning: page expired and cache-control header

Previously on this list, there have been questions about the Warning: page has expired problem. When you submit a form, then press the back button, you get this message and have to press refresh before the page will redisplay. I have discovered that if you use the following header command, the problem does not occur. header("Cache-Control: public"); The back button takes you back to the form, without a warning message, and the form redisplays with the info you entered. Does anyone know a reason that the above header should not be used? Does it cause some sort of problem that I should be aware of? Janet