Free to use would be great, and the amount of traffic the tool would regularly get could create a substantial revenue stream from just a few small non-intrusive ads.
Quick review of your JavaScript:
Your functions and variables are in a global namespace. That's not a good sign. Sure if you are absolutely sure this code will never run alongside existing code, that's okay. But if you are working with code from multiple places, that's perhaps not the wisest approach. I guess you have no long-term intentions of allowing third party plugins and modules?
You're being too-clever using commas effectively as statement separators (or maybe your JS compressor is), and boolean operators instead of if statements. Shows off that you know how to flex JavaScript, but probably concerns whether you'd be a good fit into an existing team of developers.
I wonder if concatanating chunks of strings interspersed with variables is the best course of action. I'm tempted to suggest to collate the big strings together as static text with replaceable tokens (or perhaps bring in an existing templating language like mustache).
I worry about <div class="clearDiv"> being used to clear floats. I'm surprised that blueprint forced you into that.
jQuery constructs like: $(a).parent().parent().attr("id") and $(a).parent().parent().prev are brittle, they assume/enforce a particular markup. Which means if you need that extra wrapper div, now you need to update each of those constructs.
See how HTML5BoilerPlate uses the header & footer tags: https://github.com/h5bp/html5-boilerplate/blob/master/index....
It would also be nice it you can directly output a version of html that contains all the features from HTML5BoilerPlate.
As this is the only part of the WYSIWYG editor I would use, I would go as far as to say that this is the //last// step.
It needs some more work of course but the potential is right there.
Also consider the other way round (analyze page that have been created by other means and extract the metrics)
In fact there is a whole product hidden in this, with the proper design and approach.
That said, what can you expect from a weekend project on a browser with >1% market share. Nice job! I'll probably use this.
I would enhance the UI and maybe add inline code editing for blocks in the next version.
Good luck.
