I have been wondering this myself for a while. While I believe there are probably reasons you couldn't exactly map behavior of all of today's popular scripting

I have been wondering this myself for a while. While I believe there are probably reasons you couldn't exactly map behavior of all of today's popular scripting languages into a common byte-code, you could probably approach something close to it. Part of the problem is that Webkit has a very narrow mission of wanting to only be standards compliant. This is really holding back innovation given how widely used it is in Safari and until recently Chrome. It seems to me that in order to make it happen, it would need wide support from one of the major browser vendors.