title: header element, height in em not working
body: <p>I expect the header to be 4em.. but it's smaller<br>
  why?</p>
  
  <p>My HTML is:</p>
  
  <pre><code>    &lt;header id="header"&gt;
          &lt;div class="content"&gt;
              &lt;h1&gt;&lt;?php echo $pageTitle; ?&gt;&lt;/h1&gt;
          &lt;/div&gt;
      &lt;/header&gt;
  </code></pre>
  
  <p>My css is:</p>
  
  <pre><code>header#header{
      background-color: #e9e9e9;
      height: 4em;
  }
  
  #header#header .content{
      max-width: 1200px;
      margin: 0 auto;
      height: 4em;
  }
  #header h1{
      margin: 0;
      padding: 0;
      height: 4em;
      font: bold 1.5em/4em arial;
  }
  </code></pre>