Just use a PHP include. That way your navigation (& menus) will be the same throughout your entire site, if you ever need to edit the navigation all you have to do is open up that include file, save it, upload it - and boom! its updated for your entire site.
Just make sure the path is a absolute URL, such as:
<?php include("/includes/navigation.php"); ?>
Remember too, if the include contains only HTML & Javascript than you don't need any <?php ?> tags inside the include. Just make its extension .php incase you ever decide to add PHP code to the nav in the future, because you most likely will. 🙂
Oh yeah.. the include will only work on pages which you've got named .php, but I assumed you have a PHP web site already since your posting on a PHP board.