This is exactly what I needed at the right time.

In particular, I've only recently realized that working in blocks makes the design process go much more smoothly.

What does "working in blocks" mean?

Not new (as claimed by title, and therefor flagging), but it is a useful collection of docs for people learning advanced CSS, so upmoding.

"If you flag something, please don't also comment that you did."

http://www.ycombinator.com/newsguidelines.html

If I haven't seen it before, it's new to me.

Sure, so I have no problem having it posted.

But don't call it new just because it's new to someone - everything is new to someone. Call it new only if it's new to just about everyone.