Universal Undo, Please!

Oh boy oh boy oh boy oh boy. If this blog wasn't PG-13 rated :-) I can tell you that previous sentence would have contained less three-letter words and a lot more with four letters. So I was typing up this long blog post (not this one here, but a different one), and a few minutes out from my last save I hit some combination of keys and -- bam -- my firefox window is gone (I have no idea what keys I pressed, but I'm pretty sure it didn't involve 'ALT-F, X').

Isn't it about time we had a universal undo capability? Along the lines of "If you can do it, you can undo it". So if I accidentally close down firefox, I can bring it up exactly how it was -- same windows, same window state (e.g. scrolled to the same position within the window, and so on. And the same for any other application - and for any other action you can do, inside or outside of an application.

I know there are technical issues here. At the same time, I think that a lot of them are the legacy of software and frameworks that we're stuck with for the time being at least (..yeah, I know that description is a bit vague.. but too much effor to try and make it clearer), and I think that there are places where, with a bit of effort, the scope of undo could be extended. But anyway, it doesn't seem worth my while to get into more technical details about this, so I'll leave it at that.