View http://blog.alexmaccaw.com/css-transitions
CSS3 is, quite frankly, a Really Big Deal. It hit me like a ton of bricks a couple projects ago just how much faster I'm able to develop on the front end thanks to CSS advancements alone. Depending on whether or not you bundle font-face within that we're pretty much made in the shade at this point.
By far one of the more exciting features of modern CSS are transitions. Hardware accelerated, stable animations baked right into the browser are a really good thing. Not only do they add that extra layer of awesome to our websites, they help us to clean up our code too. Being able to trigger animations simply by changing a class, for example, cuts out a ton of JavaScript for me, and just feels more stable at the end of the day.
Knowing all you can about transitions will be a wise use of time, definitely check out this article to get started.