<style>
.nav{ width: 200px;height: 50px; background-color: red;text-align: center; }
.nav_1{width: 200px;height: 50px; background-color: #ccc;text-align: center;display: none;}
.nav:hover .nav_1 {display: block;}
</style>
</head>
<body>
<div class="nav">菜单</div>
<div class="nav_1">子菜单</div>
</body>
![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
A detailed description is below. Otherwise, I really don’t understand what you are talking about. What is not displayed?