I can see your local web servers

Nope, you can't

    Cross-Origin Request Blocked: The Same Origin Policy disallows reading the remote resource at http://localhost/. (Reason: CORS header ‘Access-Control-Allow-Origin’ missing)

Anyway

    TypeError: /(192\.168\.[0-9]+\.)[0-9]+/.exec(...) is null i-can-see-your-local-web-servers:169:41

The Cross-Origin check be circumvented via DNS Rebinding: When you request mypage.com, my DNS returns the ip of my webserver. On all subsequent requests, it will return 127.0.0.1. Now localhost is on the same origin as my page.

It doesn't matter, you should be in control of a DNS the user relies on and you should have your server send

    Access-Control-Allow-Origin: mypage.com

or

    Access-Control-Allow-Origin: * 

which is not a default anywhere AFAIK and is domain based, not IP based

And your server should be enabled to respond to mypage.com host header

Based on m12k's suggested interpretation of your comment:

> you should be in control of a DNS the user relies on

You always are when a users visits your domain – you control the DNS of your domain.

> Access-Control-Allow-Origin: *

You don't need access-control headers, because you stay on the same domain.

> Your server should be enabled to respond to mypage.com host header

Most servers listening on localhost ignore the host header.