Failed to load resource: net::ERR_FILE_NOT_FOUND loading json.js

Remove the first / in the path. Also you don't need type="text/javascript" anymore in HTML5.

This error means that file was not found. Either path is wrong or file is not present where you want it to be. Try to access it by entering source address in your browser to check if it really is there. Browse the directories on server to ensure the path is correct. You may even copy and paste the relative path to be certain it is alright.

I got the same error using:

<link rel="stylesheet" href="//fonts.googleapis.com/css?family=Source+Sans+Pro:400,400i,700,700i,900,900i" type="text/css" media="all">

But once I added https: in the beginning of the href the error disappeared.

<link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Source+Sans+Pro:400,400i,700,700i,900,900i" type="text/css" media="all">