What are the top 9 essential CSS skills?

According to Acomment.net, the 9 essential CSS skills are:

1. Styling CSS layouts
2. Styilng lists
3. Understanding the box model
4. Typography
5. Forms
6. CSS Frameworks
7. Optimization and best practices
8. CSS hacks and tricks
9. Buttons, boxes and rounded corners

This is a great list, but personally, I think that learning CSS layout is critical for the modern professional designer as is understanding the box model. Optimization is next most important, because if your CSS isn't optimized (and I include commented in that definition) then you won't be able to work easily with other designers. Styling lists, forms, and typography are important, but less so. Buttons, boxes, rounded corners, and frameworks are all nice to have, but not vital. And I think that people should avoid CSS hacks as much as possible - sticking to valid CSS that does the job as well as you can in the browsers you need to support.