弹出窗口在屏幕中央

 function openBrWindowInCentre(theURL,width,height) {
      var left, top;
      left = (window.screen.availWidth - width) / 2;
      top = (window.screen.availHeight - height) / 2;
      var per = 'width=' + width + ',height=' + height + ',left=' + left + ',top=' + top + ',screenX=' + left + ',screenY=' + top;
      window.open(theURL,'',per);
    }