There are a whole slew of them...

InVision — A lot of good features, good cust. service as well

Macaw.co — They tout themselves as flexible as an image editor, but writes semantic HTML and succinct CSS

Webflow.com — Another Drag and Drop style site for creating professional responsive websites

Adobe Muse — A turn-key solution for creating and hosting websites

Adobe Reflow — Dedicated app to create responsive websites, meant for “designers to share their responsive design intent

Google Web Designer — Originally meant for creating engaging HTML5 ads, GWD can also be used to create sites with the of ease of a Drag and Drop style editor

Others... Pixate - Mobile Prototyping(still in beta I think) Flinto - Mobile Prototyping Marvelapp.com – (also still in beta)

From a client's perspective I think it comes down to the level of support you provide.

For a prototype you specify the browser level compliance and extent of the functionality (happy path all the way to fully dynamic).

When delivering a product the client usually dictates the browser level compliance and full functionality is assumed.

Its a good point, I think there are two issues you are brining up: 1. Should the concept of a "fold" exist 2. IF one is True, then can we call it something more applicable.

I think the notion of a "fold" isn't an issue as it previously was. Most people know to scroll a page. But there are some patterns that inform the user that there is more content on a page. Specifically, if you have a horizontal section that spans the entire width of a page at the bottom of a viewable page, then that could be perceived as the end. However, if you break up that strong horizontal with a column then it becomes less of an issue.

As for what to call the "fold" how about defining the viewable section as the Viewport?

Great setup experience, I did notice that my computer unlocked when I dropped (and not far) my onto my desk it unlocked. I did also notice you have to slow down your knock a bit. But I had no qualms about throwing down the 4 bucks to check it out.

SASS

NIce! I was wondering if this could be done in CSS.