<!DOCTYPE html>
<html>
  <meta charset="utf-8">
  <title>CSS Multi-column Layout Test Reference: Test column-span:all under HTML details tag</title>
  <link rel="author" title="Ting-Yu Lin" href="tlin@mozilla.com">
  <link rel="author" title="Mozilla" href="http://www.mozilla.org/">

  <style>
  details {
    column-count: 1;
    column-rule: 6px solid;
    width: 400px;
    outline: 1px solid black;
  }
  h3 {
    /* column-count: 1 makes this behave like a real spanner. */
    outline: 1px solid blue;
  }
  </style>

  <body>
    <details open>
      <summary>Columns</summary>
      <h3>spanner</h3>
      <div>block</div>
    </details>
  </body>
</html>