demo/dropbutton.html

<!DOCTYPE html>
<html>
<head>
<title>下拉菜单实例|菜鸟教程(runoob.com)</title>
<meta charset="utf-8">
<style>

.dropdownComponent {
    position: relative;
    display: inline-block;
}

.dropdownComponent:hover .dropContent {
    display: block;
}

.dropdownComponent:hover .dropBtn {
    background-color: #3e8e41;
}

.dropBtn {
    background-color: #4CAF50;
    color: white;
    padding: 16px;
    font-size: 16px;
    border: none;
    cursor: pointer;
}

.dropContent {
    display: none;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
}

.dropContent a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
}

.dropContent a:hover {
    background-color: #f1f1f1
}

</style>
</head>
<body>

<h2>下拉菜单</h2>
<p>鼠标移动到按钮上打开下拉菜单。</p>

<div class="dropdownComponent">
  <button class="dropBtn">下拉菜单</button>
  <div class="dropContent">
    <a href="http://www.runoob.com">菜鸟教程 1</a>
    <a href="http://www.runoob.com">菜鸟教程 2</a>
    <a href="http://www.runoob.com">菜鸟教程 3</a>
  </div>
</div>

<h2>测试文字</h2>

</body>
</html>