var setHeight = function () {
	var containerHeight = $('container').getHeight();
	var windowHeight = 0;
	if (self.innerHeight) {
			windowHeight = self.innerHeight;
	}
	else if (document.documentElement && document.documentElement.clientHeight) {
			windowHeight = document.documentElement.clientHeight;
	}
	else if (document.body) {
			windowHeight = document.body.clientHeight;
	}

	var diff = windowHeight - containerHeight;
	var marginTop = (diff / 2) - 5;
	if (diff > 0) {
		$('container').setStyle({ margin: marginTop + 'px auto 0 auto' });
	}
}
Event.observe(window, 'load', function(){
	setHeight();
}); 
Event.observe(window, 'resize', function(){
	setHeight();
});