完善下拉框细节（小箭头、阴影）
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>百度一下，你就知道</title>
<link rel="stylesheet" type="text/css" href="static/css/style.css">
<link rel="stylesheet" type="text/css" href="static/layui/css/layui.css">
<link rel="icon" type="image/icon-x" href="static/images/logo2.jpg">
</head>
<body>
<ul class="header">
<li><a href="http://news.baidu.com/">新闻</a></li>
<li><a href="">hao123</a></li>
<li><a href="">地图</a></li>
<li><a href="">视频</a></li>
<li><a href="">贴吧</a></li>
<li><a href="">学术</a></li>
<li><a href="">登录</a></li>
<li class="menu"><a href="">设置</a>
<div class="menu_l">
<div class="j"></div>
<a href="">搜索设置</a>
<a href="">高级搜索</a>
<a href="">关闭预测</a>
<a href="">隐私设置</a>
</div>
</li>
<li class="menu_list"><span>更多产品</span></li>
</ul>
</body>
</html>
/*下拉菜单*/
.menu{position: relative;}
.menu_l{width: 65px;/*border: 1px solid #ccc;*/
text-align: center;font-weight: normal;
line-height: 25px;
position:absolute;top: 26px;left: -20px; /*绝对定位*/
box-shadow: 1px -1px 15px #AFADAD;/*设置阴影*/
display: none;
}
.menu_l a{text-decoration: none;font-size: 12px;display: block;}
.menu_l a:hover{background: #3388FF;color:#fff; }
/*小箭头 */
.menu_l .j{width: 0;height: 6px;border:6px solid;
border-color: transparent transparent #fff transparent;
position: absolute;top: -18px;left:26px;
}
.menu:hover .menu_l{display: block;}
