*{margin:0;padding:0;}
body{font-size: 14px;font-family: "微软雅黑";}
ul,li{list-style: none;}
#app{width: 500px;height:440px;border:1px solid #ddd;margin: 30px auto;}
ul{overflow: hidden;}
.a li{float: left;width: 100px;background:#ddd;height: 40px;line-height: 40px;text-align: center;cursor: pointer;}
.a li.on{background: #fff;}
.b li{width: 500px;height:400px;text-align: center;line-height: 400px;}
.hide{display: none;}