$(function() {
	$(window).scroll(function(){
		var winTop = $(window).scrollTop();
		var winHeight = $(window).height();
		var alertHeight = $(".alert").css("height").replace(/px/,"");;
		var top  =  winTop +  winHeight/2 - alertHeight/2;
		$(".popUp").css("height",winTop+winHeight);
		$(".alert").css("top",top);
	});
});