Most Effective Menu for a CSS Template?

I'm quite new to CSS but keen to learn quickly, I'm working on making a sort of online CV website for myself and I'm working from a CSS template I've sourced online.

I immediately see if I want to makes changes to my site menu titles then I have to make the changes across every page, is there not a more efficient way I can do this from a central location?

I've heard of server-side includes but I don't think it's the right solution, can anyone help?

Many thanks

re: Most Effective Menu for a CSS Template?

If, for example, the site is about gems, instead of giving them their real names such as:
Cairngorm
Calcite
Carnelian
Cassiterite
Cerussite
Cat's-Eye Chrysoberyl
Chalcedony
Charoite
Chiastolite
Chrome Tourmaline
Chrysoberyl
Chrysocolla
Chrysoprase
label them such that they are generic and interchangeable, as in:

.c1,.c2,.c3,.c4,.c5,.c6,.c7,.c8, and so on. And best bet to change from one location is to use SSI.