window.onscroll = scroll;
function scroll(){	
	var div=document.getElementById("menuOverlay");
	var browser=navigator.appName; 
	if (browser=="Microsoft Internet Explorer"){ 
		var scrollFunction=document.documentElement.scrollTop;
	} else { 
		var scrollFunction=window.pageYOffset;
	}

	if (scrollFunction>181){
		div.style.visibility="visible";
	} else {
		div.style.visibility="hidden";
	}
}