title: Applying background color to an empty div
body: <p>I just started working on a new website, and I'm just trying to map out where everything will go. I made a few divs of the stuff I want.  When trying to add the background color to them in CSS it doesn't apply the color.</p>
  
  <p>HTML <br></p>
  
  <pre><code>&lt;body&gt;
      &lt;div class="header"&gt;&lt;/div&gt;
      &lt;div class="hero"&gt;&lt;/div&gt;
      &lt;div class="ads"&gt;&lt;/div&gt;
      &lt;div class="content-1"&gt;&lt;/div&gt;
      &lt;div class="content-2"&gt;&lt;/div&gt;
      &lt;div class="form"&gt;&lt;/div&gt;
      &lt;div class="footer"&gt;&lt;/div&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p>CSS <br></p>
  
  <pre><code>html {
      font-family: 'Muli', sans-serif;
  }
  
  .header {
      width: 100%;
      height: 20%;
      background-color: #7fffd4ad;
  }
  </code></pre>