下拉菜单模拟效果图：
CSS3：
<style>
#box{width:200px; height:50px; overflow:hidden; cursor: pointer; transition: all 0.35s;}
#box:hover{height:250px;}
#box ul{list-style:none; margin:0; padding:0;}
#box ul li{width:198px; height:48px; line-height: 50px; text-al
