A D3 map with basic interaction

hello map

<html>
<head>
    <meta charset="utf-8">
    <title>A D3 map with basic interaction</title>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
    <script src="ky-counties.js"></script>
    
    <link href="https://fonts.googleapis.com/css?family=Montserrat" rel="stylesheet" type="text/css">
<style>
    body {
        padding: 0;
        margin: 0;
        background: whitesmoke;
    }
    h1, h2 {
        position: absolute;
        left: 20px;
        top: 10px;
        font-family: "Proxima Nova", Montserrat, sans-serif;
        font-size: 2em;
        font-weight: 100;
        color: #005DAA; /* offical UK Kentucky blue */
    }
    h2 {
        top: 50px;
        font-size: 1.6em;
    }
    .county {
      stroke: #fff;
      fill:#005DAA;
    }
    .hover {
        fill: yellow;   
    }
</style>
</head>
<body>
    <h1>Kentucky Counties</h1>
    <h2></h2>
  <script>
        
    var width = 900,
        height = 600;
    
    var svg = d3.select( "body" )
          .append( "svg" )
          .attr( "width", width )
          .attr( "height", height );
      
    var projection = d3.geo.albers()
        .center([0, 37.8])
        .rotate([85.8,0])
        .scale(8000)
        .translate([width / 2, height / 2]);

var geoPath = d3.geo.path()
        .projection(projection);
        
    svg.append("g")
        .selectAll("path")
        .data(counties.features)
        .enter()
        .append("path")
        .attr( "d", geoPath )
        .attr("class","county")
        .on("mouseover", function(d){
            d3.select("h2").text(d.properties.NAME);
            d3.select(this).attr("class","county hover");
        })
        .on("mouseout", function(d){
            d3.select("h2").text("");
            d3.select(this).attr("class","county");
        });
 
  </script>
</body>
</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js