Javascript 浏览器在桌面上的位置


    <script language = "javascript" type = "text/javascript">
          var Gemotery = {};
          if (window.screenLeft) { //IE and others
              Gemotery.getWindowX = function() { return window.screenLeft; };
              Gemotery.getWindowY = function() { return window.screenTop; }
          } else if (window.screenX) {//Firefox and others
          Gemotery.getWindowX = function() { return window.screenX; };
          Gemotery.getWindowY = function() { return window.screenY; }
      }
      //Execute
      var winX = Gemotery.getWindowX();//Error
      var winY = Gemotery.getWindowY();//Error
      document.write("x="+winX+",y="+winY);
      </script>
上面的错误在什么地方啊。求救！！