The unregister() method was used to ask the system to unregister and delete the specified endpoint. In the updated API, a subscription is can be unregistered via the PushSubscription.unsubscribe() method.
document.load() is a part of an old version of the W3C DOM Level 3 Load & Save module. Can be used with document.async to indicate whether the request is synchronous or asynchronous (the default). As of at least Gecko 1.9, this no longer supports cross-site loading of documents (Use XMLHttpRequest instead).