I am assuming you mean when the file is not in the hype resources.
This is a security thing in regards to Cross-origin resource sharing ( CORS ) and is the main reason I put the file in the resources to show in the example how things work.
But basicly Browsers will block loading files that origins are different from the main site unless you have things setup to do so on your server.
So trying to load a file from a local HD can prove to be a pain. a few browsers have menus you can use to disable the checks so you can develope..
This is a big subject so It is best you google it to find out how it works as there is a lot out there.
ps I added a v2 file to the multiple md file post