batmanjs.org is run on GitHub pages, and uses Jekyll.
To test your changes locally, gem install jekyll and jekyll serve, then check out http://localhost:4000.
The API docs are generated from a set of literate CoffeeScript files in the main batman.js repository.
To generate them yourself, make sure you've cloned the main repo, and execute the following command from within your copy of the batmanjs.github.io repo.
cd batmanjs.github.io # or wherever you keep it
npm install # if you haven't installed the dependencies before
bin/generate_docs --dir <path to the main batman.js repo>/docs