This philosophy of "designing in the browser" is what our product is based on. We believe strongly that you're a better web designer if you know how to write HTML and CSS and our prototyping tool's features are built for people like that (eg. like us).

Here are two relevant blog posts we wrote while establishing our direction and attitude about 6 months ago:

* http://blog.quplo.com/2010/04/our-philosophy-design-in-the-b... - what designing in the browser is, why we think it's important, and some other references to thought leaders talking about it.

* http://blog.quplo.com/2010/04/why-were-not-building-yet-anot... - why we think the world doesn't need yet another WYSIWYG, drag-and-drop "prototyping" tool.

Anyway, if you subscribe to the Mockup-in-Markup idea, check out our app, Quplo. It's an online app where you write HTML and CSS and a little custom markup language specifically made for prototypes (eg. <page>, <layout>, <var> etc). You can import an existing website and redesign it quite easily; everything you make is accessible from yourprototype.quplo.com (with or without a password). If you like it, head to http://dev.quplo.com/freeupgrade for a free beta-period upgrade to a higher plan!