title: Position: fixed with vertical space
body: <p>What I have is a rather basic issue with position: fixed.</p>
  
  <p>Here's a sample:</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-css lang-css prettyprint-override"><code>* {
      margin: 0;
      padding: 0;
  }
  .nav {
      width: 100%;
      height: 50px;
      background: #000;
      position: fixed;
  }
  
  .content {
      background: #ccc;
      width: 100%;
      height: 5000px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="nav"&gt;&lt;/div&gt;
  &lt;div class="content"&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;test&lt;br /&gt;&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>What I want is the scrolling to start <strong>below</strong> the black bar (with a fixed position).</p>