<header>：Header 元素

<header>
  <a class="logo" href="#">Cute Puppies Express!</a>
</header>

<article>
  <header>
    <h1>Beagles</h1>
    <time>08.12.2014</time>
  </header>
  <p>
    I love beagles <em>so</em> much! Like, really, a lot. They’re adorable and
    their ears are so, so snugly soft!
  </p>
</article>

.logo {
  background: left / cover
    url("/shared-assets/images/examples/puppy-header.jpg");
  display: flex;
  height: 120px;
  align-items: center;
  justify-content: center;
  font:
    bold calc(1em + 2 * (100vw - 120px) / 100) "Dancing Script",
    fantasy;
  color: #ff0083;
  text-shadow: black 2px 2px 0.2rem;
}

header > h1 {
  margin-bottom: 0;
}

header > time {
  font: italic 0.7rem sans-serif;
}

<header>
  <h1>Main Page Title</h1>
  <img src="mdn-logo-sm.png" alt="MDN logo" />
</header>

<article>
  <header>
    <h2>The Planet Earth</h2>
    <p>
      Posted on Wednesday, <time datetime="2017-10-04">4 October 2017</time> by
      Jane Smith
    </p>
  </header>
  <p>
    We live on a planet that's blue and green, with so many things still unseen.
  </p>
  <p><a href="https://example.com/the-planet-earth/">Continue reading…</a></p>
</article>