window.onresize = function(){
	var x = $(window).getSize().x;
	var y = $(window).getSize().y;
	var boxw = parseInt($('preloader_container').style.width) / 2; 
	var boxh = parseInt($('preloader_container').style.height) / 2;

	var align = Math.round(x / 2 - boxw);
	var valign = Math.round(y / 2 - boxh);

	$('preloader_container').style.marginLeft = align + 'px';	
	$('preloader_container').style.marginTop = valign + 'px';
}