Fix screen reader skip-to-content link

Author: jake-low

_layouts/page.html

@@ -38,7 +38,7 @@ <h3>Screencasts</h3>
   </ul>
 </nav>
 
-<main id="#content">
+<main id="content">
 {% if page.title %}
   <h1>{{ page.title }}</h1>
 {% endif %}