If you want to break those bad habits and get ahead with CSS, make sure you have this set of resources bookmarked.
So, you're feeling thoroughly chastened after reading about the 10 CSS mistakes that every web designer must avoid, and you're keen sort out your CSS skills? You're in luck; here's a collection of six absolutely top-notch CSS resources that'll help you ensure that you're writing the best, cleanest code imaginable.
HTML5 Rocks: Tutorials
Besides having great primers on how browsers work, HTML5 Rocks releases tutorials at least once a month about how to do things better in browsers.
Sass's @extend functionality
Sass, and particularly its @extend function, can help you move more towards component-based CSS and away from many of the bad habits mentioned in this article. Check out the documentation to find out how it works and see for yourself how powerful it can be.
Optimise browser rendering from Google
A classic reference on rendering best practices, loaded with information on how browsers render, helping you better know the browser and write better CSS.
Michael Labriola discusses browser rendering as it relates to performance. This hour-long session and other videos from this year's Adobe MAX are available online, and worth a watch.
W3C's CSS tips about units
The W3C has a collection of CSS examples available, including an interesting tidbit about units.