Here is a small preview of a very helpful article that Jared Ponchot wrote at Lullabot about "Desiging - in the browser".
"To me, suggesting that good design for web can only be done "within the browser" is akin to suggesting that good architectural design can only be done with 2x4's. On the flip side, suggesting that a web designer doesn't need to know and understand rudimentary things like HTML markup and CSS to design well for browsers is also like suggesting an architect need not know anything about how buildings get built in order to design one. Here be dragons!
I think the key point is that mockups and markup are just one small part of a broader design process. This is a process that should begin not in mockups or markup, and that often ends in something more complex and varied than simple markup as well. Many websites today are services with multiple interfaces, not all of which are built on markup or rendered in browsers. I'll soon be publishing articles on various aspects of our design process here at Lullabot, so I'll save more for another day on that."