So instead of writing Javascript, we would build our own browsers to download alongside the HTML? Or failing that would have to offer some prepackaged browser.

So instead of writing Javascript, we would build our own browsers to download alongside the HTML? Or failing that would have to offer some prepackaged browser. And every device, from a smartphone to a 30" screen running on an octo-Xenon would have to be able to execute the same native code. And each vendor of a browser kit would try to establish their own web standards to go with their home-grown engine. I am pretty sure this is not the future of the web, and this seems like a great thing. And it's not like this is a completely novel idea. None of the proprietary sandboxed browing environments of the past (Flash, Silverlight...) made anything really easier. They sometimes enabled us to do things that were impossible with HTML+JS, but they were all both a pain in the lower back for developers and users and had glaring security holes.