function launchExercise(url)
{
	var str = "toolbar=0,menubar=0,location=0,scrollbars=0,fullscreen=1,titlebar=0,status=0,channelmode=0";
	var win = window.open(url, "exercise", str);
	win.focus();

	document.fire("exercise:launched", { url: url });
	
	new PeriodicalExecuter(function(pe) {
		if(win.closed) {
			pe.stop();
			document.fire("exercise:closed", { url: url });
		}
	}, 1);
	
	return false;
}