P3P Policy not working to allow 3rd party cookies in IE

The policy checker at http://www.webentrust.com/p3p.html says Error: No P3P Policy Found

You are saying, in the p3p header, this:

P3P: policyref="/w3c/p3p.xml", CP="IDC DSP COR NID DEVi OUR BUS INT"

meaning "I have this compact policy (CP), and also this full policy: /w3c/p3p.xml". BUT, http://www.hankshelper.com/w3c/p3p.xml (referenced above) gives a 404 Not Found error. You have to create your p3p policy - e.g. using the IBM P3P Editor and upload it to the path you specified.

I'm not certain what part of our original compact policy was being rejected, but I was finally able to solve this problem with the help of couple other resources.

From here: http://www.marco.org/2007/04/27/p3p-sucks-how-to-get-frame-cookies-unblocked-in-ie6

This is approximately the minimum HTTP header needed, and it basically says “We’re not collecting any of your personal data”:

P3P: CP=”NID DSP ALL COR”

If you actually store some data, such as email addresses and login cookies, this (also working) policy may be more correct:

P3P: CP=”ALL ADM DEV PSAi COM OUR OTRo STP IND ONL”

The policy we ended up using was

ALL ADM DEV PSAo COM OUR OTRo IND ONL

Descriptions of all the compact policy parameters can be found here: http://www.p3pwriter.com/LRN_111.asp