Long live CSS!
I write fiction stories, and I've got a website I publish them on. And, a few months ago, I got a request to make the text bigger, to make it easier to read, for those who don't have their reading glasses handy.
So I made a copy of the entire site, and then, by changing only two lines in the main external style sheet, I created over 200 pages of large print edition all in one swoop.
How cool is that!