window.postMessage Test

One Parameter `window.postMessage("Test 1")` This should throw an exception.
*2nd Parameter: ""** `window.postMessage("Test 2", "*")` This should work, but fails in IE8.
window.attachEvent `window.postMessage("Test 3", "http://stevesouders.com")` This should work, but fails in IE8.
document.attachEvent `window.postMessage("Test 4", "http://stevesouders.com")` This is the only implementation that works in both IE8 and FF3.

This page provides a demonstration of window.postMessage. It's in the HTML 5 spec. It's implemented in Internet Explorer 8 and Firefox 3, but the implementation in IE8 deviates from the spec.

Test 1 should thrown an exception. The HTML 5 spec says, "If the value of the targetOrigin argument is neither a single U+002A ASTERISK character ("*") nor a valid URI or IRI, then throw a SYNTAX_ERR exception...". Even though the second parameter is missing, IE8 doesn't thrown an exception.
Test 2 should work, but it fails in IE8. The HTML 5 spec says, "If the value of the targetOrigin argument is neither a single U+002A ASTERISK character ("*") nor a valid URI or IRI, then throw a SYNTAX_ERR exception...". Even though "*" is valid according to the spec, IE8 still throws an exception and aborts. The workaround I found was to use a valid URI, but this negates the cross-domain communication benefits of postMessage.
Test 3 should work, but it fails in IE8. The HTML 5 spec says, "When a script invokes the postMessage(message, targetOrigin) method on a Window object,...". But postMessage only works when it's attached to the document object.