i dont know what ive changed

header.js

@@ -42,6 +42,7 @@ class Header extends HTMLElement {
         <li><a href="operating_systems/index.html">Operating Systems</a></li>
         <li><a href="social_platforms/index.html">Social Platforms</a></li>
       </ul>
+    </div>
     `;
   }
 }