Uh huh ... that’s exactly my reaction, too.

Then, when you start peeking at the source-code of the thing, you discover an XSLT document, and a small one at that, which is drawing data from XML data-sources.   Included in that output is just a couple of very small JavaScript onclick and mouseover routines, just for effect.   The HTML that you see is generated, and it’s being done by your browser!

Another, much more inaccessible, example of XSLT is DocBook, which is the technology that enabled all those O’Reilly books (the ones with animals on the cover ...) to be produced in all those different forms.   You suspected that the same material was being drawn-from over and over again, and so it was.   You suspected that the extremely-regular formatting of the books was generated, somehow.   And it was, and this is how.   Not through programming, but through XSLT.   Online help, slide shows, all sorts of things, are produced this way.

(And I’ve done a lot of it ... happy to consult.)