I have a facebook app that uses iframe.
facebook loads my website inside an iframe. When I click a link, my website display an iframe using lightbox to display a faceboo
If u r still looking for solution then try building P3P headers http://www.p3pwriter.com/LRN_121.asp
usually there is a security issue when setting cookies inside iframe, p3p headers act as an agreement between website and client's computer guaranteeing that the information saved in cookies wont be misused.
quick solution: http://planet.admon.org/how-to-implement-p3p-http-headers-for-cross-site-cookies/
what to do: copy paste this in your header:
<?php
header('P3P: CP="CURa ADMa DEVa PSAo PSDo OUR BUS UNI PUR INT DEM STA PRE COM NAV OTC NOI DSP COR"')
?>
thats it!