My navigation bar is in the body tag. Entire code for navigation bar is in nav.html file (without any html or body tag, only the code for navigation bar).
<script src="https://code.jquery.com/jquery-1.10.2.js"></script>
Then in the body tag, a container is made with an unique id and a javascript block to load the nav.html into the container, as follows:
<!--Navigation bar-->
<div id="nav-placeholder">
</div>
<script>
$(function(){
$("#nav-placeholder").load("nav.html");
});
</script>
<!--end of Navigation bar-->