After I read this article, what I understand is that in order to allow cross-domain ajax calls, I have to set the server response to be Access-Control-Allow-Origin:
May be these lines of code solve your problem.
You can do one thing for that just need to set Access-Control-Allow-Origin & Access-Control-Allow-Headers in CustomeHeaders your web service web.config file.
If you want to allow only for specific domain , you can do that with specific value of domain instead of * value