I think what you’re trying to do is have a single file for your menu, which you can update once and then include it on all your web pages?
You could consider using an “include” command – see here
for a basic explanation. This would allow you to have one file including your menu html, and then a statement in each web page which imports the menu html into the rest of the page. I’m not too familiar with this but this might point you in the right direction.
A possible alternative, if you are using some sort of web editing package like Dreamweaver, is to make use of the template functionality where you would effectively save the menu as a template and then use it as the basis for all the other pages.
Hope this helps. Maybe others can suggest other ways of doing what you’re after.