http://viralpatel.net/blogs/2008/12/how-to-set-third-party-cookies-with-iframe.html

How to set third-party cookies with iframe?

I had problem with the lead base ad click tracking. I was using the iFrame to track the lead information from the advertiser site. But somehow IE is not sending any cookie information from there. Infect firefox also doesn’t send any cookie information for the first request (i.e. when the iFrame src page is called) but if you call any page from the main file (i.e. specified in the source for iFrame like image or script src), I get the cookies.

What are third-party cookies?

If you put your code on other website using iFrame which calls pages from your site, then the cookies groups are called third party cookies (as both the domains, main page source and iFrame source, are different). Other examples of third party cookies are images or other objects contained in a Web page may reside in servers different from the one holding the page. In order to show such a page, the browser downloads all these objects, possibly receiving cookies. These cookies are called third-party cookies if the server sending them is located outside the domain of the Web page.

Some browsers allow third party cookies and in some browsers, like Internet Explorer, it depends on the privacy settings of the browser. In IE6 (Internet Explorer 6) with the default privacy setting of ‘Medium’, third party cookies will be deleted.

As it turns out, there is a simple solution. If you supply a ‘compact privacy policy’ with your page, then IE will treat the cookies with respect and let them through.

The code

Just add this to the start of your page (every page where cookies will be written):

How to set p3p http header in ASP.Net?

HttpContext.Current.Response.AddHeader("p3p", "CP=\""IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT\""")

How to set p3p http header in PHP?

header('P3P:CP="IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT"');

How to set p3p http header in JSP?

response.setHeader("P3P","CP='IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT'")

How to set p3p http header in ColdFusion?

<cfheader name="P3P" value="CP='IDC DSP COR ADM DEVi TAIi PSA PSD IVAi IVDi CONi HIS OUR IND CNT'" />

The above code will set P3P (Platform for Privacy Preferences Project) header. It allows the browser (specially Internet Explorer) to through all the third-party cookies (which may be set through iFrame).