This web page is a demo to show how does navigator.registerProtocolHandler work. This page installed web+github custom protocol through registerProtocolHandler with a below code.
The HTML 5.2 specification is https://www.w3.org/TR/html52/webappapis.html#dom-navigatorcontentutils-isprotocolhandlerregistered
If you click this link, it runs web+github: protocol: this
[After registerProtocolHandler] web+github protol is
Now is time to test unregisterProtocolHandler for web+github:
window.navigator.unregisterProtocolHandler("web+github",
"https://gyuyoung.github.io/CustomSchemeExample/%s", "title");