console 命令行工具 X clear
console
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div.header, 
        div.footer {
            height: 100px;
            background-color: gray;
        }

        .left {
            height:500px;
            width:50%;
            float:left;
            background-color: red;
        }

        .right1,
        .right2 {
            height:250px;
            width:50%;
            float: left;
        }

        .right1{
            background-color: yellow;
        }
        
        .right2 {
            background-color: blue;
        }

        .clerarfix:after {
            content:"";
            display: table;
            clear:both;
        }

        h1{
            margin:auto auto;
            width:300px;
            line-height:100%;
        }
    </style>

</head>

<body>

    <div class="header">
        <h1>header</h1>
    </div>

    <div class="content clearfix">
        <div class="left">
            <h1>left</h1>
        </div>
        <div class="right1">
            <h1>top-right</h1>
        </div>
        <div class="right2">
            <h1>bottom-right</h1>
        </div>
    </div>
    <div class="footer">
        <h1>footer</h1>
    </div>
    
</body>
</html>