And JS can also indirectly initiate requests for resource or page fetches, e.g. by creating image tags or popup windows. It can't see the results directly, but it can make some inferences.
There are ways, but they generally need a cooperation of both sides of the inter-domain boundary. What you generally can't do is make arbitrary reads from the context of other domain (e.g. call GET on their api and read a result) into your domain without them explicitly allowing it.
Right. What you can sometimes do is observe the effects of the content being loaded, e.g. see the dimensions of an image element change when its content is loaded.
oh hell yes. And oh yes iframes and postmessages, of course people would setup them incorrectly and even if they do some (probably not that important but still) data will leak if you're creative enough. Thanks for the link!
