dream-serve is a very simple server for static sites. It reloads your browser when the site changes.
It's good for developing docs, streamlining coverage reports, and so forth. It works by injecting a script into HTML, which opens a WebSocket back to the server. The server uses the WebSocket to tell the browser when to reload.
opam install dream-serve
To choose a port number,
dream-serve ./my/site -p 9090