MAPG-87 use HTML5 semantic elements, new styles, new footer

views/error/404.php

@@ -1,7 +1,6 @@
 <?php require ROOT . '/views/templates/main_header.php'; ?>
 <?php require ROOT . '/views/templates/header.php'; ?>
-<div class="main">
     <h2>404 | Page not found</h2>
     <p>The requested URL was not found on this server. <a href="/" title="MapGuesser">Back to start.</a></p>
-</div>
+<?php require ROOT . '/views/templates/footer.php'; ?>
 <?php require ROOT . '/views/templates/main_footer.php'; ?>