Added .BaseURL to link in 404 page

layouts/404.html

 
     <div class="content container">
       <h1>404: Page not found</h1>
-        <p class="lead">Sorry, we've misplaced that URL or it's pointing to something that doesn't exist. <a href="/">Head back home</a> to try finding it again.</p>
+        <p class="lead">Sorry, we've misplaced that URL or it's pointing to something that doesn't exist. <a href="{{ .Site.BaseURL }}">Head back home</a> to try finding it again.</p>
     </div>
 
   </body>