If you hand code CSS and don’t have a Mac, you should get one just for the unbelievably great application Xyle Scope. I can honestly say that for a CSS code poet, that app is worth buying a Mac for. (The Mac will pay for itself in with the hours of productivity saved thanks to the application and the environment, I swear it!)
The DOM Inspector isn’t really all that user-friendly, but with some curious clicking on various buttons, icons and nodes in the tree, you can find several useful things to play with. Also, if you double-click any of the CSS values in the DOM Inspector, a window pops up and allows you to temporarily change the value for an instantly visible preview result. Swanky!
It doesn’t hold a candle to the power, grace and features of Xyle Scope for CSS examination, but for a free and readily available tool for any platform that can support Firefox, I guess it’s a gem. 🙂