title: Want to set background color of my menu item
body: <p>Here is my HTML code:</p>
  
  <pre><code>&lt;nav id="nav"&gt;
   &lt;ul&gt;
    &lt;li&gt;
     &lt;a href="#"&gt; Home &lt;/a&gt;
    &lt;/li&gt;
    &lt;li&gt;
     &lt;a href="#"&gt; About Us &lt;/a&gt;
    &lt;/li&gt;
    &lt;li&gt;
     &lt;a href="#"&gt; Photos &lt;/a&gt;
    &lt;/li&gt;
    &lt;li&gt;
     &lt;a href="#"&gt; Contact &lt;/a&gt;
    &lt;/li&gt;
   &lt;/ul&gt;
  &lt;/nav&gt; 
  </code></pre>
  
  <p>what code should I do for changing its background colour?</p>