function showPopup() {
		 var winW = 1024;
		 var popup_width = 401;

		 if (parseInt(navigator.appVersion)>3) {
		  if (navigator.appName=="Netscape") {
			winW = window.innerWidth;
		  }
		  if (navigator.appName.indexOf("Microsoft")!=-1) {
			winW = document.body.offsetWidth;
		  }
		 }
		 var popup = document.getElementById("popup_layer");
		 popup.style.left = Math.round((winW-popup_width)/2)  + "px";
		 popup.style.visibility = "visible";
	  }
	  function hidePopup() {
		 var popup = document.getElementById("popup_layer");
		 popup.style.visibility = "hidden";
	  }