How to change part of a website through many pages?

I have a website with a set of rollover tabs on the top for different parts of the website. I have about 50 total pages on the website that all display these tabs. I now need to add a new tab to that list and have the change show up on all the pages. Is there any way to do this just once and have the rest of them adopt the change? I originally made the pages by making one html page and saving variations of it.How to change part of a website through many pages?
Includes is the answer to your problem. However, if you haven't used includes then you will have to edit all 50 files anyway. But if it is likely to change again in the future, using includes will save you a lot of work.How to change part of a website through many pages?
If you use include files all you have to do is change the include file and not the 50 pages if not then you have to manually change all 50.