I'm not aware of any way of doing it in HTML, but if you were to do it in PHP, it's simple enough, if you had a certain nav bar you wanted included in every page you'd just put:
Putting the HTML code in a seperate page for the nav, and the PHP would automatically slam it in there each time. And you don't have to know PHP to make PHP pages per se, you can just use general HTML markup in a PHP file and it'll work fine.
