Earlier this year, Digital Web Magazine started a column called Web Design 101. The series is written in a way that is helpful for those who are just getting started but also useful as a reference and review for more experienced designers.
The most recent article in this series discusses the float property, which I have always found to be one of the trickiest CSS properties to fully understand. It’s a pretty well-written and comprehensive piece, and the same could be said of the rest of the Web Design 101 series.