old_contents:  function main() {
           var map = new L.Map('map', {
               zoomControl: false,
               center: [44.908, -75.83],
               zoom: 15
           });
           L.tileLayer(
               'http://server.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer/tile/{z}/{y}/{x}', {
                   attribution: 'Tiles &copy; Esri &mdash; Esri, DeLorme, NAVTEQ',
                   maxZoom: 16
               }).addTo(map);
           // load 10k course route
           $.getJSON("10k.geojson", function(data) {
               // add GeoJSON layer to the map once the file is loaded
               L.geoJson(data).addTo(map);
           });
           // load 10k course route features
           $.getJSON("features.geojson", function(data) {
               //add GeoJSON layer to the map once the file is loaded
               L.geoJson(data, {
                   style: function(feature) {
                       return {
                           color: "green"
                       };
                   },
                   pointToLayer: function(feature, latlng) {
                       return new L.CircleMarker(latlng, {
                           radius: 10,
                           fillOpacity: 0.85
                       });
                   },
                   onEachFeature: function(feature, layer) {
                       layer.bindPopup(feature.properties.cng_Meters);
                   }
               }).addTo(map);
           });
       }
       // you could use $(window).load(main);
   window.onload = main;
new_contents:  function main() {
           var map = new L.Map('map', {
               zoomControl: false,
               center: [44.908, -75.83],
               zoom: 15
           });
           L.tileLayer(
               'http://server.arcgisonline.com/ArcGIS/rest/services/Canvas/World_Light_Gray_Base/MapServer/tile/{z}/{y}/{x}', {
                   attribution: 'Tiles &copy; Esri &mdash; Esri, DeLorme, NAVTEQ',
                   maxZoom: 16
               }).addTo(map);
           // load 10k course route
           $.getJSON("10k.geojson", function(data) {
               // add GeoJSON layer to the map once the file is loaded
               L.geoJson(data).addTo(map);
           });
           // load 10k course route features
           $.getJSON("features.geojson", function(data) {
               //add GeoJSON layer to the map once the file is loaded
               L.geoJson(data, {
                   style: function(feature) {
                       return {
                           color: "red"
                       };
                   },
                   pointToLayer: function(feature, latlng) {
                       return new L.CircleMarker(latlng, {
                           radius: 10,
                           fillOpacity: 0.85
                       });
                   },
                   onEachFeature: function(feature, layer) {
                       layer.bindPopup(feature.properties.cng_Meters);
                   }
               }).addTo(map);
           });
       }
       // you could use $(window).load(main);
   window.onload = main;
subject: update marker