It can be done in several ways in several places. Websites created in this sort of way are usually very badly-constructed when it comes to the html that has been generated. There will be a LOT of code that:
(a) Does nothing.
(b) Does something, but badly and in an over-complicated way.
(c) You cannot fathom.
(d) Does something OK, but very slowly.
Why not try to construct the website using the html you can understand? You'll learn a whole lot about html, websites and of course, you won't put the watermark in.
AND it's fun.
(Incidentally, you can learn a lot about website coding and construction by looking at the code for this site. It's not particularly sophisticated, but it's nice and tight and easy to understand).