小编Tom*_*sen的帖子

.section {
  width: 100%;
}

.section .container {
  background-color: #fff;
  width: 250px;
  margin: 0 auto;
  text-align: center;
}

.section .container::before {
  background-color: red;
  content: ' ';
}

.section .container::after {
  background-color: blue;
  content: ' ';
}

.section .container h1 {
  padding: 10px;
}

<div class="section">
  <div class="container">
    <h1>Hello world.</h1>
  </div>
</div>