小编yuy*_*raj的帖子

body {
  height: 500px;
  width: 80%;
  margin-top: 0;
  margin-bottom: 0;
  margin-left: auto;
  margin-right: auto;
  padding: 0;
  background-color: lightgray;
}
.header {
  width: 80%;
  height: 100px;
  margin-left: auto;
  margin-right: auto;
  background-color: yellow;
  /* border: solid 1px black; */
}

<div class="header">
  <ul>
    <li><a href="index.html">Dashboard</a></li>
  </ul>
</div>