Header("Cache Control: must-revalidate");

Hi Ya All!, It is found that when I use the HTML, Javascript & PHP script, things work fine. Then when it come to printing, that's when I found an interesting errors. The errors is not the printer, it is how the webpage is being cached. This website use the SSL and authication to access the database. As I narrow down the problem to the webpage that use "POST" operation within the form where you enter data and press the button to execute the webpage. It is found that once the "POST" is executed, then hte this same webpage is not cached, it just expired. The odd thing is that it work in Internet Explorer and that it doesn't work in Netscape Navigator. So, I decide to include the " header("Cache Control: must-revalidate"); " to see if it would work. Instead I get the error saying " Warning: Cannot add header information - headers already sent by (output started at /user_index.php:45) in /user_index.php on line122 " I looked up in the script and I don't see any problem because I only use one header script, it is on line 122 and there is no other header script on this web script. So, what seem to be the problem? If I should not be using this script then what can I do about resolving hte Cache expiring issues? Any help would be greatly appreciated. From the website I have read is that "POST" and SSL, they both do not allow the caching by default or whatever does the website meant by that. Thanks, Scott Fletcher