Construct HTML fragments with the constuctors of the Htmlit.El module and render them to strings. Here's a simple example to get you started.
open Htmlit
let abbrs =
[ "KISS", "Keep it simple, stupid";
"DRY", "Don't repeat yourself" ]
let abbrify ?(at = []) (a, exp) = El.abbr ~at:(At.title exp :: at) [El.txt a]
let page ?(footer = El.void) ~title contents =
let body = El.body [El.h1 [El.txt title]; contents; footer] in
El.page ~lang:"en" ~title body
let mypage () =
let comma = El.txt ", " in
let abbrs = El.splice ~sep:comma (List.map abbrify abbrs) in
let content = El.p [El.txt "Keep in mind: "; abbrs; El.txt "."] in
page ~title:"Hints" content
let main () = print_endline (El.to_string ~doctype:true (mypage ()))
let () = if !Sys.interactive then () else main ()