There is a tutorial in pdf format, that pretty much starts with hello world:

https://www.mercurylang.org/documentation/papers/book.pdf

  :- module hello.
  :- interface.
  :- import_module io.
  :- pred main(io::di, io::uo) is det.
  :- implementation.
  main(IOState_in, IOState_out) :-
    io.write_string("Hello, World!\n", IOState_in, IOState_out).

Is the problem that this is pdf, rather than html?