title: No 'Access-Control-Allow-Origin' header is present on the requested resource Error when loading JSON file
body: <p>My dataset is hosted on my dropbox account but not the Javascript files calling it.
  I am working with D3 and Polymaps to visualize the data, however I get an error saying - "XMLHttpRequest cannot load <a href="https://www.dropbox.com/s/89adzt973quosda/solaruse.json" rel="noreferrer">https://www.dropbox.com/s/89adzt973quosda/solaruse.json</a>. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'null' is therefore not allowed access."
  (the link to the dropbox file works so you can have a look see)</p>
  
  <p>Here is the code I used to load the JSON file (I am developing the site locally)
  I'm not exactly sure what to do from this point.</p>
  
  <pre><code>var po = org.polymaps;
          //Create map object, append to #map
          var map = po.map()
              .container(d3.select("#map").append("svg").node())
              .zoom(4)
              .add(po.interact());
          // Add the CloudMade image tiles as a base layer…
          map.add(po.image()
              .url(po.url("http://{S}tile.cloudmade.com"
              + "/1a1b06b230af4efdbb989ea99e9841af" // http://cloudmade.com/register
              + "/998/256/{Z}/{X}/{Y}.png")
              .hosts(["a.", "b.", "c.", ""])));
          // Add the compass control on top.
          map.add(po.compass()
              .pan("none"));
          // Add the custom locations/acres
          d3.json("https://www.dropbox.com/s/89adzt973quosda/solaruse.json", function(data){
              // Insert layer beneath the compass.
              var layer = d3.select("#map svg").insert("svg:g", ".compass");
              // Add an svg:g for each Name.
              var marker = layer.selectAll("g")
                  .data(d3.entries(data))
                  .enter().append("svg:g")
                  .attr("transform", transform);
              // Adding the circles
              marker.append("svg:circle")
              //function scraping the acres from the dataset
              .attr()
          });
  </code></pre>