I recently stumbled upon one of the best web design tutorials that I have seen in some time. No matter if you are a beginner or an experienced developer, I would highly recommend spending the time to work through the entire series.
The series is broken up into two parts. Part one, Design a Warm, Cheerful Website Interface in Adobe Photoshop, is a walk-through tutorial that walks the reader through the process of creating a web design using Photoshop. Even if you do not own Photoshop, the tutorial is very informative and helps the reader understand how designers create new designs. I especially liked the use of the 960 Grid System.
Part two, Convert a Warm, Cheerful Web Design to HTML and CSS, is a video series explaining how to take the previously created web design and convert it into HTML and CSS. The author incorporates many of the new features of HTML 5 and CSS3 and even explains how these new features are rendered in older browsers. He even further explains how the 960 Grid System aids in rapid web development.
As of this post, both tutorials are free of charge.