We\'re building a Facebook application here at work, using the iframe method. For the application to work, it needs to set cookies from within the iframe.
Safari has thi
Rather than targeting the browser, target the behaviour.
Set the cookie and on the next page-load check for them with your JS. If they're not there, set them with the alternative method.
(And make sure you don't end up in an infinite loop for users without cookies)
Edit: Hmm if FF can't read them that might be an issue. How about sending everybody through this system?