function popup(page,popupname,height,width)
	{
	var topPosition = (screen.height - height) / 2;
	var leftPosition = (screen.width - width) / 2;
	var windowprops = "width=" + width + ",height=" + height + ",top=" + topPosition + ",left=" + leftPosition + ",location=no,menubar=no,toolbar=no,scrollbars=no,resizable=no,status=no";
	newWindow = window.open(page,popupname,windowprops);
	}

function isset(varname)
	{
  if(typeof( window[ varname ] ) != "undefined") return true;
  else return false;
	}