I have a contact form inside of an iframe, which uses captcha, and therefore requires session variables. It works fine in every browser except IE9. To make it work in IE8, I added the following line at the beginning of the php document:
header('P3P:CP="CAO IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"');
However, this doesn't appear to work in IE9. Any ideas?