With new versions of our trusted browsers coming out, web developers who like living on the edge can start using some of the new features that are becoming available. One such goody is cross-document messaging, which is part of the HTML5 draft spec.
On the downside (as if security is not a problem); this brand new feature is only available in Firefox 3 for now. My own little test (a copy of John Resig’s example with some minor tweaks) worked in Opera 9.2x (and 9.5b) as well, but postMessage seems to have been dropped from the final Opera 9.5, as the tests on Opera Labs don’t seem to work any more either. Support for postMessage is also available in Webkit (Safari‘s backbone) nightly builds and in Microsoft’s IE 8 BETA (with the event being ‘onmessage’ instead of ‘message’ and some other quirks but hey, this is beta, no?).
So expect postMessage to be available in all major browsers by the end of the year. But why wait if you know that Facebook is already using postMessage in their chat application. I wonder what they fall back to if it is not available though …