design template?

Hi all 

I am about to design my first decent size web page and would like some
advice.  There are many design with menu on the left panel and detail on the
right panel.  I would like the menu to remain the same throughout and the
detail in the right panel changes when a menu item is selected.  The submenu
would pop up when I place the mouse on top of the item.

Does this mean that I will end up with one html file for each new page?
This means a large portion of the html code for each page will be the same.
If so, when I add or change a menu item, does this mean that I would edit
each html page?  

Regards
Ming Lam