老师，请帮我看一下3-3代码，总感觉有些不对劲，但是又不知道是哪里不太对？谢谢老师

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<style type="text/css">
    /*此处写代码*/
    *{margin:0;padding:0;border:0;font-family:"微软雅黑";}
      .header,
      .footer{
          width:100%;
          height:100px;
          line-height: 100px;
          text-align: center;
          background: #000;
      }
      a{text-decoration: none;color:#fff;}
      ul{list-style-type: none;}
      .logo{
          float: left;
          width:30%;
          height:100px;
      }
      .nav{
          float: right;
          width: 70%;
          height: 100px;
      }
      .nav:hover{
          color:orange;
          cursor:pointer;
      }
      .nav li{
          list-style-type: none;
          display:inline-block;
          float:right;
          margin-right: 30px;
      }
      .footer li{
          display:inline-block;
          margin-right: 30px;
      }
      .container{
          width: 100%;
          min-height: 500px;
          text-align: center;
      }
      .middle,
      .left,
      .right{
          position: relative;
          float:left;
          height: 500px;
      }
      .middle{
          margin-left: 25%;
          width: 50%;
          background: pink;
      }
      .middle img ,
      .left ul,
      .right ul{
          margin:10% auto;
          text-align: left;
      }
      .left{
          width: 25%;
          margin-left: -100%;
          left:25%;
          background: #f5deb3;

      }
      .left a{
          color:black;
          background-color: orangered;
      }
      .left li,.left span,.right li{margin-left: 20px;line-height: 50px;}
      .right{
          width: 25%;
          background-color: aqua;
      }
      input{
          height: 40px;
          width:250px;
          border:none;
      }
      .red{background-color: red;}
</style>
</head>
<body>

<div class="header">
      <div class="logo">
          <img src="http://img1.sycdn.imooc.com/climg//58c0d2d900016ce303000100.png">
      </div>
      <div class="nav">
          <ul>
              <li><a href="#">课程</a></li>
              <li><a href="#">职业路径</a></li>
              <li><a href="#">实战</a></li>
              <li><a href="#">猿问</a></li>
              <li><a href="#">手记</a></li>
          </ul>
      </div>
</div>
<div class="container">
      <div class="middle">
          <img src="http://img1.sycdn.imooc.com/climg//590037e00001fab706000400.jpg">
      </div>
      <div class="left">
          <ul>
              <li><h4>课程推荐</h4></li>
              <li><a >职业路径</a><span>HTML5与CSS3实现动态网页</span></li>
              <li><a>职业路径</a><span>零基础入门Andriod语法与界面</span></li>
              <li><a >职业路径</a><span>ios基础语法与常用控件</span></li>
              <li><a>职业路径</a><span>PHP入门开发</span></li>
              <li><a >职业路径</a><span>JAVA入门开发</span></li>
          </ul>
      </div>
      <div class="right">
          <form>
              <ul>
                  <li><h4>登陆</h4></li>
                  <li><input type="text" placeholder="请输入登陆邮箱/手机号" name="username"></li>
                  <li><input type="password" placeholder="6-12位密码，不要空格" name="password"></li>
                  <li><input type="submit" value="登陆" name="submit" class="red"></li>
              </ul>
          </form>
      </div>
</div>
<div class="footer">
      <ul>
              <li><a href="#">网站首页</a></li>
              <li><a href="#">企业合作</a></li>
              <li><a href="#">人才招聘</a></li>
              <li><a href="#">联系我们</a></li>
              <li><a href="#">常见问题</a></li>
              <li><a href="#">友情链接</a></li>
      </ul>
</div>
</body>
</html>