Very nice - smooth and fast. Suggestions for version 0.2 and beyond, in increasing order of utility:

Reset/Reset All buttons might be better named Undo and Reset Page.

The element selector at the top left goes gray when I have a UX element highlighted for editing. This makes it seem like an inactive cosmetic element because I'm used to things being greyed out. It took me a few minutes to notice it as a button on first use; all my attention was on the target page when selecting a UX element to edit, and when I looked back at Stylebot I went straight to the modifiers. As you put a green highlight around the currently selected CSS element, perhaps not turn the button green rather than the same color as its parent?

Beginner Mode for consumers - 'Hide This', 'Bigger/Smaller', or a 'Simplify!' slider, that goes to Readability-like simplicity over 5 stages. Not essential, I just thought the basic layout was still a bit 'busy' for newbies...but then you don't want to be troubled with newbie-type support requests. It's a good layout - but as above, there are so many options that I completely overlooked an important aspect of the selection interface.

(Windows only?) UX element highlight is static. Many TextArea controls can be freely resized, eg this comment box on HN (which was probably designed to promote comment brevity...). If I make the box larger while it's highlighted the highlight doesn't follow. Not a big deal, but...

...it made me wish I could drag things around to rearrange the layout. There's a little tool for that called LiquidPage: http://www.alexschreyer.net/programming/liquid-page-a-bookma... LiquidPage and Stylebot would make a lovely couple. They should get married. They should have children.

Presets. If you can save a page look, why not share it with other users? Let people share their setups like themes. Gives you web traffic as well as downloads, stickiness, and repeat visitors. Could later be an outlet to sell a more complex tools aimed at professional; or could also be a source of intelligence site managers would pay for - '93% of Stylebot users hide your sidebar, but nobody seems to mind your topline menu.' Their gratitude would make up for the inevitable hate mail from designers.

That's so important I'm going to say it again. Let people share their layouts. Most of them will be lame and you will wonder why you bothered. Then one day someone will make a much better 'look' for some popular website and it will spread like wildfire. People will install Stylebot just so they can use this fabulous new layout for a site they visit every day but secretly hate looking at. This will be controversial, which means lots of media exposure. The famous website will fire the designer and hire the Stylebot layout creator. Users who liked the original design will revolt. The original designer will release his/her own Stylebot skin, with many improvements that /she had always wanted to add but not been allowed to. Designwars will begin on every popular website. Some site admins will try to ban Stylebot, others will be delighted stop wasting time on stuff they were never very good at anyway and focus on content instead of presentation.

Let people build presets that aren't tied to any particular website, just collections of parameters for different basic CSS elements. Let people paint them onto existing pages from a palette - select an existing 'clean' or 'fancy' button style and then start painting it onto the buttons that are on a page, rather than adjusting their settings one by one.

There are opportunities along the way to work with something like Balsamiq or Wordpress or other content/layout creation services. Users could select or tweak CSS to their heart's content at the client end and upload the results to the page - but that that is justs a sideshow to the main event.

At some point you will need to think of a way to easily filter themes on your website before your users do, because there will be a tidal wave of Myspace-type 'sparkle artists' busy remaking the look of the web with glitter, Comic Sans, and animated Velvet Elvis icons. Fortunately, the rest of us won't have see any of that, but the best/worst of these 'artists' will inexplicably be able to make a living from selling their hideous creations to other people with questionable taste. By that stage, a few hardcore designers will stop sending you hate mail and start recruiting ninja assassins to destroy Stylebot forever, but it will be too late, and ultimate layout control will have gone to the dark, er, client side.

I jest a little, but I've already decided I will not be going back to the 'old' Craigslist.