function getScrollY() {
  scrOfY = 0;
  if( typeof( window.pageYOffset ) == 'number' ) {
    //Netscape compliant
    scrOfY = window.pageYOffset;
  } else if( document.body && ( document.body.scrollLeft || document.body.scrollTop ) ) {
    //DOM compliant
    scrOfY = document.body.scrollTop;
  } else if( document.documentElement && ( document.documentElement.scrollLeft || document.documentElement.scrollTop ) ) {
    //IE6 standards compliant mode
    scrOfY = document.documentElement.scrollTop;
  }
  return scrOfY;
}


function overlay() {
	
	var offset = getScrollY();
	var h = screen.height;
	t = (h/2) + offset;
	
	el = document.getElementById("overlay");
	el.style.top = offset+'px';
	el.style.visibility = (el.style.visibility == "visible") ? "hidden" : "visible";
	
	var msg = document.getElementById("msg");
	msg.style.visibility = (msg.style.visibility == "visible") ? "hidden" : "visible";

	var nuevoX = t - 180;
	
	msg.style.top = nuevoX + 'px';

	
	//msg.style.top = nuevoX + 'px';
	
	/*
	if (men.length > 0)
	{
		document.getElementById("txt").innerHTML = men + "<br /><br />";
	}
	*/
}