再看老是教程的同时，自己操作进行
<!DOCTYPE html>
<html lang="zh">
<head>
<meta charset="utf-8">
<title>作业</title>
<link rel="stylesheet" type="text/css" href="css/第一节.css">
<link rel="stylesheet" href="css/font-awesome-4.7.0/css/font-awesome.min.css">
</style>
</head>
<body>
<div class="header">
<div class="header_content">
<div class="header_left">
<a class="header_a" href="">中国大陆 <i class=" fa fa-angle-down"></i></a>
<a href="" style="color:#ff5000 ">亲，请登录</a>
<a href="">免费注册</a>
<a href="">手机逛淘宝</a>
</div>
<div class="header_right">
<a href="" class="header_a"><span style="color:#ff5000"></span>我的淘宝<i class=" fa fa-angle-down"></i>
<ul>
<li>已买到的宝贝</li>
<li>我的足迹</li>
</ul>
</a>
<a href="" class="header_a" class="fa fa-shopping-cart" >购物车</a>
<a href="" class="header_a"><span class="fa fa-star" style="color:#ff5000"></span>收藏夹<i class=" fa fa-angle-down"></i>
<ul>
<li>收藏的宝贝</li>
<li>收藏的店铺</li>
</ul></a>
<a href="" class="header_a">商品分类</a>
<a href="" class="header_a">卖家中心<i class=" fa fa-angle-down"></i>
<ul>
<li>免费开店</li>
<li>已卖出的宝贝</li>
<li>出售中的宝贝</li>
<li>卖家服务市场</li>
<li>卖家培训中心</li>
<li>体检中心</li>
<li>问商友</li>
</ul>
</a>
<a href="" class="header_a">联系客服<i class=" fa fa-angle-down"></i></a>
<a href="" class="header_a"><span class="fa fa-reorder " style="color:#ff5000"></span>网站导航<i class=" fa fa-angle-down"></i></a>
</div>
</div>
<div class="clear"></div>
</div>
</body>
</html>
下面是CSS
*{margin: 0px;padding:0px}
a{text-decoration: none;color: rgb(0,0,0); font-size: 13px}
li{list-style: none;}
.clear{clear: both;}
.header{width: 100%;background-color: #f5f5f5}
.header_content{width: 1200px;margin: 0px auto;line-height: 40px}
.header_left{height: 40px;float: left;}
.herder_left a{margin-right: 5px}
.header_content a:hover{color: #ff5000}
.header_right{height: 40px;float: right;}
.header_a{display: inline-block;height: 40px; width:9px;text-align: center;width: 90px;position: relative;}
.header_a:hover{background-color: #fff;}
.header_a ul{border: 1px solid #f5f5f5;display: none;border-top: none}
.header_a:hover ul{display: block;position: absolute;width: 100px;}
.header_a ul li:hover{background: #f5f5f5;}
.header_a ul li{color: #6c6c6c;height: 30px;line-height: 30px;text-align: left;padding: 0px 3px;margin: 5px 0px;}