On Mac safari facebook app not returning the current users details
Safari 3rd party cookie iframe trick no longer working? I have faced this same problem while developing the Facebook application.
I found a good stuff in stack overflow
<IfModule mod_headers.c> Header set P3P "policyref=\"/w3c/p3p.xml\", CP=\"NOI DSP COR NID CUR ADM DEV OUR BUS\"" Header set Set-Cookie "test_cookie=1" </IfModule>