I have to upgrade old web site, the one big problem is menu on the right side.

It has at least 20 menu buttons - pages, and when they need to do simply update, they need to update each (20) pages.

I would like to put something, which will remove that each page has it's own menu, something like single file to update and that will reflect to all pages.

What is the best thing to do, can you give me some directions, links, or any help.

I can provide more info, just let me know.