My website has the same navigation menu throughout, instead to rewriting the HTML code for every page, can I link to a second HTML file (that contains the nav HTML code) lik
That is called HTML includes, and YES, it is possible
My HTML include will go here.
NOTES
HTML doesn't have a simple include mechanism (except for frames like iframe, which have side effects).
A better solution would be to use Server-Side includes, which is the preferred way of adding common parts to your document, on the server, of course.