iFrame的妙用作为弹出层铺底覆盖

var iframe = U.isie6() ? '<iframe style="position:absolute;left:0;top:0;z-index:2000000;filter:Alpha(opacity=0); width:100%;height:' + ds.height + '" frameborder="0"></iframe>' : '';
$container.append(iframe).appendTo($body);