You should use php for including all your headers,footers etc. You can use it even if you do not have any knowledge about php. Follow the link here -> http://www.w3schools.com/php/php_includes.asp . The includes are server-side. When the user requests for your website, php copies all your includes and pastes it to the main-file and then sends data to the user.
For example
//the php file
<?php
include "header.html";
include "footer.html";
?>
The header.html file =>
<div class="header">...</div>
The footer.html file =>
<div class="footer">...</div>
The output =>
<div class="header">...</div>
<div class="footer">...</div>