howto 在线编辑器 | howto代码测试

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1">
<style>body {
  margin: 0;
  font-family: Arial, Helvetica, sans-serif;
}

.topnav {
  position: relative;
  overflow: hidden;
  background-color: #333;
}

.topnav a {
  float: left;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  font-size: 17px;
}

.topnav a:hover {
  background-color: #ddd;
  color: black;
}

.topnav a.active {
  background-color: #4CAF50;
  color: white;
}

.topnav-centered a {
  float: none;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
}

.topnav-right {
  float: right;
}

/* 响应式导航菜单（适用于移动设备）*/
@media screen and (max-width: 600px) {
  .topnav a, .topnav-right {
    float: none;
    display: block;
  }
  
  .topnav-centered a {
    position: relative;
    top: 0;
    left: 0;
    transform: none;
  }
}
</style>
</head>
<body>

<div class="topnav">

<div class="topnav-centered">
    <a href="#home" class="active">首页</a>
  </div>
  
  
  <a href="#news">News</a>
  <a href="#contact">联系方式</a>
  
  
  <div class="topnav-right">
    <a href="#search">Search</a>
    <a href="#about">About</a>
  </div>
  
</div>

<div style="padding-left:16px">
  <h2>具有居中和右对齐链接的响应式顶部导航</h2>
  <p>调整浏览器窗口大小以查看响应效果。</p>
</div>

</body>
</html>

报个问题: