function positionVerticalAlignMiddle(id) {
	var innerHeight = 0;
	if (self.innerHeight) { // all except Explorer
		innerHeight = self.innerHeight;
	} else if (document.documentElement && document.documentElement.clientHeight) { // Explorer 6 Strict
		innerHeight = document.documentElement.clientHeight;
	} else if (document.body) { // all other Explorers
		innerHeight = document.body.clientHeight;
	}
	var node = document.getElementById(id);
	var marginTop = (innerHeight - node.offsetHeight) / 2;
	if (marginTop < 0) marginTop = 0;
	node.style.marginTop = marginTop+'px';
}