IE7-CrossBrowser-Cookie-Fix-For-Facebook.php

/* 
Some IE7 browsers reject cross-domain cookies inside an iframe Facebook app 
which causes authentication issues. If IE is blocking your cookies you'll see 
a little red icon at the bottom of the browser.

This thread has a good overview:
http://forum.developers.facebook.net/viewtopic.php?pid=156383#p156383

To fix it:
1) Create a P3P privacy policy XML file using this online tool: 
http://www.webentrust.com/p3ptools/editor/templates.html

2) Edit the p3p.xml file and update the URIs to point at the privacy policy for your site

3) Upload the file to /w3c/p3p.xml on your server

4) Run the P3P policy validator against it and fix any errors.
http://validator.w3.org/p3p/20020128/policy.pl?uri=http://yourserver.com/w3c/p3p.xml

5) In your site's code, set these HTTP headers using PHP before any content is sent. Make sure policyref points at your xml file.
*/

<?php 
header('Content-Type: text/html; charset=utf-8');
header('P3P: policyref="/w3c/p3p.xml", CP="HONK"');
?>

/*
6) If you're still getting blocked, you can test your CP codes using this tool:
http://www.webentrust.com/cpp.html

*/