Sorry if this is an obvious question. I don't know where to look for an answer or what this might be called. My last experience with HTML was from the HTML 3.0 days. 
Let's say I have a few static HTML pages on a site. They are all supposed to have the same "look." They all link to the same CSS file, and I've designed them similarly etc. But I am wondering if it is possible to define common "code chunks" and just reference these chunks from each individual page. E.g. so that if I change a chunk, I change every page that uses that chunk. It would sure beat going through 8 different HTML files to adjust some tiny little property in my site-wide footer every time I want to do that.
Let's say I have a few static HTML pages on a site. They are all supposed to have the same "look." They all link to the same CSS file, and I've designed them similarly etc. But I am wondering if it is possible to define common "code chunks" and just reference these chunks from each individual page. E.g. so that if I change a chunk, I change every page that uses that chunk. It would sure beat going through 8 different HTML files to adjust some tiny little property in my site-wide footer every time I want to do that.