Webkit is the rendering engine that runs Apple Safari and Google Chrome. Analogously, Trident powers IE and Gecko powers Firefox. Webkit, however, is by far the most advanced of the three (with Trident being a distant third).

Webkit supports some awesome advanced CSS features, including advanced selectors and animations. Check out some of these examples in Chrome or Safari 4 – the fact that all this is done without Javascript and Flash is simply amazing. Adding color transition events on mouse hover, for instance, is as simple as a single line in your CSS declaration:

-webkit-transition: color 1s ease-in-out;

Enhancements like this are progressive-style enhancements – they aren’t supported everywhere, but they likely will be in the web of the future (minus the ‘-webkit’ identifier), and they don’t take much away if they aren’t present.