W3School TIY 亲自试一试！

<!DOCTYPE html>
<html>
<head>
<style>
body {margin:0;}

ul {
  list-style-type: none;
  margin: 0;
  padding: 0;
  overflow: hidden;
  background-color: #333;
  position: fixed;
  bottom: 0;
  width: 100%;
}

li {
  float: left;
}

li a {
  display: block;
  color: white;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

li a:hover:not(.active) {
  background-color: #111;
}

.active {
  background-color: #4CAF50;
}
</style>
</head>
<body>

<ul>
  <li><a class="active" href="#home">Home</a></li>
  <li><a href="#news">News</a></li>
  <li><a href="#contact">Contact</a></li>
  <li><a href="#about">About</a></li>
</ul>

<div style="padding:20px;background-color:#1abc9c;height:1500px;">
  <h1>固定的底部导航栏</h1>
  <h2>请滚动页面以查看效果。</h2>
  <h2>页面滚动时导航栏将位于页面底部。</h2>

</body>
</html>

W3School TIY Editor