Non Working Youth Map

<!DOCTYPE html>
<html lang="en">
	<head>
		<meta charset="utf-8">
		<title>Mercator projection</title>
		<script type="text/javascript" src="//d3js.org/d3.v3.min.js"></script>
		<style type="text/css">

body {
				background-color: gray;
			}

svg {
				background-color: white;
			}

</style>
	</head>
	<body>
		<script type="text/javascript">

//Width and height
			var w = 500;
			var h = 300;

//Define map projection
			var projection = d3.geo.mercator()
								   .center([ 0, 40 ])
								   .translate([ w/2, h/2 ])
								   .scale([ w/7 ]);

//Define path generator
			var path = d3.geo.path()
							 .projection(projection);

//Create SVG
			var svg = d3.select("body")
						.append("svg")
						.attr("width", w)
						.attr("height", h);

//Load in GeoJSON data
			d3.json("youthmaps.json", function(json) {
				
				//Bind data and create one path per GeoJSON feature
				svg.selectAll("path")
				   .data(json.features)
				   .enter()
				   .append("path")
				   .attr("d", path);
		
			});

</script>
	</body>
</html>

https://d3js.org/d3.v3.min.js