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>
</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>