title: How to center an iframe horizontally?
body: <p>Consider the following example: (<a href="http://jsfiddle.net/wYNSu/" rel="noreferrer">live demo</a>)</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div&gt;div&lt;/div&gt;
  &lt;iframe&gt;&lt;/iframe&gt;
  </code></pre>
  
  <p>CSS:</p>
  
  <pre><code>div, iframe {
      width: 100px;
      height: 50px;
      margin: 0 auto;
      background-color: #777;
  }
  </code></pre>
  
  <p>Result:</p>
  
  <p><img src="https://i.stack.imgur.com/d82gb.png" alt="enter image description here"></p>
  
  <p>Why the <code>iframe</code> is not centrally aligned like the <code>div</code>? How could I centrally align it?</p>