I... um, it's a first step we took 17 years ago, didn't we? http://en.wikipedia.org/wiki/Netscape_Composer
I totally agree that browsers should allow editing. Even if you are not authorized to PUT the page back to the server, it would still be useful to be able to edit before you print or save the page locally.
I really have no idea why we were robbed of this capability! It was probably just laziness from the people who wrote mainstream browser and httpd implementations.
http://www.jwz.org/doc/groupware.html
Anyone who doesn't think the Netscape ship sank is probably too young to remember pre-Firefox (or too close to events to be objective); but the fact that the ship was salvaged from near the bottom of the ocean doesn't change the fact that it did sink.
I think the best way to start writing webpages is with a text editor - which almost any OS out there will already have, and that IDEs are like calculators - they're a great help when you already know what you're doing, but not ideal for starting out learning.
That said, if this makes it to the stable release channel it would be a big (and positive) change of direction for Mozilla, who have had a history of removing power-user-oriented features (and most developers probably started out as power users.) I remember a thread on HN (might've been about Australis?) in which others were wondering whether they would eventually remove the "View Source" function.
Small correction: they'll ask "How do I make my own apps?"
And the answer will be the same.
For example, the day I discovered that they sell surveilance cameras in regular electronics stores, I was very surprised. Up until then, I had thought that only special kinds of highly trained professionals even knew how to get them and that the whole thing was a giant unified system that cost close to infinite amounts of money.
What do you do when you run into a kid holding an iPad?
http://twolivesleft.com/Codea/
And then I'll tell him that with just a Mac (which he might already own) and a $100 dollar subscription, he can program and even sell iPad apps worldwide, to a market of half a billion people.
People seem to forget how, in those 80s computers, to get a compiler (besides the built-in BASIC one) you usually paid lots of money. And that a worldwide distribution network for your apps, with automatic payment handling et al was also out of the question. As was an SDK even 10% as complete as Cocoa Touch or the Android one.
As I've said elsewhere, a lot of kids still assume that programming is essentially "magic" done by professionals and they implicitly assume there is no way to getting started at their education level (This is especially true if their parents are non-technical, as mine were). All the resources in the world may exist, but they may not be obvious unless you look for them. When I was a kid I assumed that programmers were all professionals with a billion years of training and their own special equipment. Today I know the only difference between a programmer and a yet-to-be-programmer kid are bigger feet and a coffee addiction, the computers are the very same. But I didn't know that back then - I wish someone told me.
I think it is extremely healthy to have the lowest bar possible to go from "Hey I like that" to "Can I do that? Can I make it myself?" Putting an IDE inside the browser, having no other dependencies between viewing web-pages and making web-pages is an incredible first step.
I await the day any kid asks "How do I make my own webpages?" and we can answer "You've already got everything you need, just press F12."
There's an art to making seemingly insurmountable things appear doable, like becoming a programmer if you have no programmer role models, and I think we should give it more attention. The web makes it easier than ever, and while a bundled IDE isn't going to be the Geocities or Bob Ross equivalent, it's definitely the next step in reducing the friction of getting started.
Bravo, Firefox team.