1. .clearfix:before,.clearfix:after {
    2.   content: "";
    3.   display: table;
    4. }
    6. .clearfix:after {
    7.   clear: both;
    8. }
    10. .clearfix { /* IE6、7专有 */
    11.   *zoom: 1;
    12. }

    用法完全和 :after相同，只是代码有所修改，这里不在赘述。

    • 优点：代码更简洁
    • 缺点：要照顾低版本的浏览器

    底层原理：
    image.png

    在这里提供一下完整的代码和运行结果展示：

    <!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>清除浮动</title>
    <style>
        .clearfix:before,
          .clearfix:after {
            content: "";
            display: table;
        }

        .clearfix:after {
            clear: both;
        }

        .clearfix { /* IE6、7专有 */
            *zoom: 1;
        }

        .out {
            width: 800px;
            border-color: darkmagenta;
            border-style: solid;
            border-width: 2px;
        }

        .daMao {
            background-color: burlywood;
            width: 200px;
            height: 200px;
            margin: 0 auto;
            float: left;
        }

        .erMao {
            background-color: cornflowerblue;
            width: 200px;
            height: 200px;
            margin: 0 auto;
            float: left;
        }

        .floot {
            width: 800px;
            height: 300px;
            background-color: forestgreen;
        }
    </style>
</head>

<body>
    <div class="out clearfix">
        <div class="daMao">大毛</div>
        <div class="erMao">二毛</div>
        <div class="new"></div>
    </div>
    <div class="floot"></div>
</body>

</html>

    image.png