How do I set cookies from outside domains inside iframes in Safari?

Question

From the Apple developer faq

Safari ships with a conservative cookie policy which limits cookie writes to only the pages chosen ("navigated to") by the user.

By default Safari only allows cookies from sites you navigate to directly. (i.e. if you click on links with the url of that domainname).

This means that if you load a page from your own site with an iFrame with a page from another site, that the other site is not able to set cookies. (for instance, a ticketshop). As soon as you have visited the other domain directly, the other site is able to access and change its own cookies.

Without having access to code on the other site, how can i make the user-experience as inobtrusive as possible?

Is there a (javascript?) way to check if the other site's cookies are already set, and accordingly, show a direct link to the other site first, if needed?

Update:

The HTML5 feature 'window.postmessage' seems to be a nice solution.
There are some jQuery libraries that might help, and compatible with most recent browsers.
In essence, the iFrame document sends messages, with Json, thru the window element.

The very nice Postmessage-plugin, by daepark, which i got working.
and another jQuery postMessage, by Ben Alman i found, but haven't tested.

Answer 1

localStorage, supported by safari and all modern browsers, permits read/write operations even on pages loaded into iframes. if you don't mind dropping support for ie6 and ie7, try using localStorage instead of cookies in your framed site. i know your question specifically says you don't have access to code on the framed site, but for those who do, localStorage definitely solves the "no cookies in a safari iframe" problem.