Web browsers disable some Javascript features for security reasons.

My bet is that you just hit Google Chrome forbidding `XMLHttpRequest` on local files by default (see [this answer on SO][1] for how to disable that, but beware: this is dangerous). See [this page][2] on the Chrome dev site for details.

This is why you have to setup a local HTTP server to workaround the security lock.


  [1]: http://stackoverflow.com/questions/4819060/allow-google-chrome-to-use-xmlhttprequest-to-load-a-url-from-a-local-file
  [2]: https://developer.chrome.com/extensions/xhr