This isn’t so much a real website as it is a demonstration of what’s possible with CSS3. The site demonstrates the power of CSS transform and transition. They distort the images so that they look like files sliding together, but then when you hover over one it removes the distortion and faces forward.
It’s similar to the way iPads and iPhones display album artwork from your music collection. That same effect can be made with just CSS3. Specifically, the transform:distort property and transition. Distorting each image makes it take up less space, so not only is it an aesthetic effect, but it’s functional as well. You can fit more images on the page if they’re distorted a little bit.