float浮动没学好

 问题box-sizing 触发

结构

<div class="wrapper">
<!--            头部-->
        <header class="clearfix">
            <h2 class="fl">家电</h2>
            <span class="nav fr">
                <a href="">热门</a>
                <a href="">电视影音</a>
            </span>
        </header>
<!--        内容list-->
        <article class="list">
                <ul class=" clearfix c">
                   <li class="fl pic"> 
                      <section><a href="#"><img src="../img/livelectrion1.webp" alt=""></a></section>
                      <section><a href="#"><img src="../img/livelectrion2.webp" alt=""></a></section>
                   </li>
                </ul>
                <ul>
                   <li class="fr">
                        <section>
                            <ul>
                                <li><a href=""></a></li>
                                <li><a href=""></a></li>
                                <li><a href=""></a></li>
                                <li><a href=""></a></li>
                            </ul>
                        </section>
                        <section>
                               <li><a href=""></a></li>
                                <li><a href=""></a></li>
                                <li><a href=""></a></li>
                                <li><a href=""></a></li>
                        </section>
                    </li>
                </ul>
        </article>
<!--        bottom-->
        <footer></footer>

//样式

*{
     margin:0;
     padding: 0;
}
.wrapper{
     1226px;
    height: 686px;
    background: gray;
    margin: auto;
}

header>h2 {
    font-weight:200;
    margin:0;    
    color: #333;
    font-size: 22px;
}
.fr{
    float: right;
}
.fl{
    float: left;
}
.clearfix::after{
    content: "";
    display: block;
    clear: both;
}



a {
    text-decoration: none;
    color: black;
}



header {
     100%;
    height: 58px;
    line-height: 58px;
    border: 1px solid black;   //----> box-sizing
 　　 box-sizing: border-box;
}

.clearfix .nav>a {
    margin-left: 15px;    
}

span a {
    font-size: 13px;
    color: #424242;
}

li {
    list-style: none;
}

.list .pic img {
    display: block;
     234px;
    height: 300px;
    
}

.list {
    height: 628px;
    text-indent:;
}


article {
    height: 628px;
}

.list .c {
    margin: 0;
    padding: 0;
    height: 100%;
}