code4sac.org is run on GitHub pages, and uses Jekyll.
Once you have satisfied the pre-requisites, install the Ruby Gem dependencies:
bundle install
This will install Jekyll which is used to compile the site.
Now fire up Jekyll:
jekyll serve --watch
This will start up a web server at http://localhost:4000
that will serve the site content on your computer.
Whenever you make a change, Jekyll will automatically re-compile the site's content and it will instantly be available in your local copy for you to play with.
That's it!