You may see many sites nowadays which have beautiful CSS animations. These animations include things like fading in content, sliding in content, bouncing buttons, buttons which flip around - there are so many different types of animations now available to web designer and developers. Animations can make your site look a lot more fluid and just prettier in general. They can also benefit sites which have buttons so when a button is clicked or interacted with it shows the user that their action has worked.
My own personal site - oliur.com - uses an animation. The content fades down into the page.
If you've ever been interested in adding animations to your sites you'll definitely need to check out Daniel Eden's Animate.css resource. He has gone through the trouble of compiling a very pretty selection of animations. The animations are super easy to implement and can be done within a few seconds. These animations are even used by big sites such as EA and Foursquare.