'Access-Control-Allow-Headers': 'Content-Type' json

  
    <add name="Access-Control-Allow-Origin" value="*" />
    <add name="Access-Control-Allow-Headers" value="Origin, X-Requested-With, Content-Type, Accept" />
  </customHeaders>
</httpProtocol>

As hinted at by this post Error in chrome: Content-Type is not allowed by Access-Control-Allow-Headers just add the additional header to your web.config like so..