crossdomain.js

$(document).ready(function() {
	$.ajax({
		type: "GET",
		url: "http://www.google.com",
		dataType: 'json',
		crossDomain: true // forcing a cross domain request for demonstration, you can omit this
	})
	.done(function(content) {
		console.log(content);
	});
});

// should result in error message:
// XMLHttpRequest cannot load http://www.google.com/. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access.