title: How to vertically align div on page with flexbox
body: <p>The following is not vertically aligning the div with text in browser tab (it is horizontally aligning correctly):</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div style="height: 100%; display: flex; align-items: center; justify-content: center;"&gt;
  
    &lt;div&gt;
      Some vertical and horizontal aligned text
    &lt;/div&gt;
  
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>What is wrong?</p>