console 命令行工具 X clear
console
<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>东华H5菜鸟教程(runoob.com)</title>
    <style>
        * {
            box-sizing: border-box;
        }
        
        div {
            border-width: 20px;
            border-style: solid;
            border-color: red;
        }
        
        .box {
            width: 100%;
            height: 800px;
        }
        
        body {
            margin: 0;
        }
        
        .header {
            background-color: #2196F3;
            color: white;
            text-align: center;
            padding: 15px;
        }
        
        .footer {
            background-color: #444;
            color: white;
            padding: 15px;
        }
        
        .topmenu {
            list-style-type: none;
            margin: 0;
            padding: 0;
            overflow: hidden;
            background-color: #777;
        }
        
        .topmenu li {
            float: left;
        }
        
        .topmenu li a {
            display: inline-block;
            color: white;
            text-align: center;
            padding: 16px;
            text-decoration: none;
        }
        
        .topmenu li a:hover {
            background-color: #222;
        }
        
        .topmenu li a.active {
            color: white;
            background-color: #4CAF50;
        }
        
        .column {
            float: left;
            padding: 15px;
        }
        
        .clearfix::after {
            content: "";
            clear: both;
            display: table;
        }
        
        .sidemenu {
            width: 25%;
        }
        
        .content {
            width: 75%;
        }
        
        .sidemenu ul {
            list-style-type: none;
            margin: 0;
            padding: 0;
        }
        
        .sidemenu li a {
            margin-bottom: 4px;
            display: block;
            padding: 8px;
            background-color: #eee;
            text-decoration: none;
            color: #666;
        }
        
        .sidemenu li a:hover {
            background-color: #555;
            color: white;
        }
        
        .sidemenu li a.active {
            background-color: #008CBA;
            color: white;
        }
    </style>
</head>

<body>

    <ul class="topmenu">
        <li><a href="#home" class="active">主页</a></li>
        <li><a href="#news">新闻</a></li>
        <li><a href="#contact">联系我们</a></li>
        <li><a href="#about">关于我们</a></li>
    </ul>

    <div class="clearfix">
        <div class="column sidemenu">
            <ul>
                <li><a href="#flight">飞行</a></li>
                <li><a href="#city" class="active">城市</a></li>
                <li><a href="#island">小岛</a></li>
                <li><a href="#food">食物</a></li>
                <li><a href="#people">人民</a></li>
                <li><a href="#history">历史沿革</a></li>
                <li><a href="#oceans">海洋</a></li>
            </ul>
        </div>

        <div class="column content">
            <div class="header">
                <h1>城市</h1>
            </div>
            <h1>哈尼亚</h1>
            <p>干尼亚是克里特岛上干尼亚地区的首府。这座城市可以分为两部分，老城区和现代城市。</p>
            <p>您将在下一章中了解有关响应式网页的更多信息。</p>
        </div>
    </div>

    <div class="footer">
        <p>底部文本</p>
    </div>

</body>

</html>