老师你好!这是我的代码，能不能帮看一下还有那些需要改的地方？

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
.header {
width: 100%;
height: 100px;
background: black;
position: fixed;
top: 0;
left: 0;
overflow: hidden;
z-index: 9;
}
.img{float: left; position: relative}
.list{
font: normal 20px "Microsoft YaHei";
color: #ffffff;
line-height: 100px;
text-align: right;
}
.list span{cursor: pointer;}
.page-background{
width: 100%;
height: 2000px;
text-align: center;
background-color: rgb(173,216,230);
margin-bottom: 100px;
}
.content {
width: 70%;
height: auto;
background-color: red;
font: normal 16px "Microsoft YaHei";
position: relative;
top: 200px;
margin: 0 auto;
/*border: 1px solid red;*/
}
.banner1{
width: 40%;
height: auto;
background: transparent;
text-align: left;
line-height: 2.5em;
float: left;
/*margin-left: 150px;*/

}
.banner2 {
width: 50%;
height: auto;
background: transparent;
text-align: left;
line-height: 2.5em;
float: right;
}
.tit,.tit2{
list-style: none;
}
.color{
background-color: pink;
}
.footer{
width: 100%;
height: 100px;
background: black;
text-align: center;
line-height: 100px;
position: fixed;
bottom: 0;
font: normal 16px "Microsoft YaHei" ;
color: #fff;
}
.footer .font{
line-height: 100px;

}
.footer .font span{
cursor: pointer;
}

/*.banner1{*/
/*width: 100%;*/
/*height: 480px;*/
/*background: url("http://img1.sycdn.imooc.com/climg//58c0eda50001e12416000480.jpg") no-repeat red;*/
/*background-size: cover;*/
/*margin-top: 100px;*/
/*}*/
/*.banner2{*/
/*width: 100%;*/
/*height: 480px;*/
/*background: url("http://img1.sycdn.imooc.com/climg//58c0edb80001c9f216000480.jpg") no-repeat red;*/
/*background-size: cover;*/
/*!*margin-top: 100px;*!*/
/*}*/
/*.banner3{*/
/*width: 100%;*/
/*height: 480px;*/
/*background: url("http://img1.sycdn.imooc.com/climg//58c0edc9000100d516000480.jpg") no-repeat red;*/
/*background-size: cover;*/
/*}*/

</style>
</head>
<body>
<div class="header">
<div class="img">
<a href="#"><img src="http://img1.sycdn.imooc.com/climg//58c0d2d900016ce303000100.png"/></a>
</div>
<div class="list">
<span>课程</span>            
<span>职业路径</span>            
<span>实战</span>             
<span>猿问</span>             
<span>手记 </span>         
</div>
</div>
<div class="page-background">
<div class="content">
<div class="banner1">
<ul class="tit">
<li><h3>课程推荐</h3></li>
<li><span class="color">职业路径</span>    HTML5与CSS3实现动态网页</li>
<li><span class="color">职业路径</span>    零基础入门Android语法与界面</li>
<li><span class="color">职业路径</span>    ios基础语法与常用的控件</li>
<li><span class="color">职业路径</span>    PHP入门开发</li>
<li><span class="color">职业路径</span>    JAVA入门开发</li>
</ul>
</div>
<div class="banner2">
<ul class="tit2">
<li><h3>相关课程</h3></li>
<li>HTML    CSS    Javascript</li>
<li>HTML5    CSS3    Jquery</li>
<li>移动端基础    移动端APP开发</li>
</ul>
</div>
</div>
</div>
<div class="footer">
<div class="font">
<span>网站首页</span>      
<span>企业合作</span>      
<span>人才招聘</span>      
<span>联系我们</span>      
<span>常见问题</span>      
<span>友情链接</span>      
</div>
</div>
</body>
</html>