How to Create a Torn Page Effect in Photoshop?
That image is a combination of torn paper and page curl.
Spoongraphics.co.uk has excellent tutorials for both components:
I tried the Photoshop way first, but I was never satisfied with the results. The problem I faced was not the end results didn't look good(in that faux way), but because they just didn't look "real." So what I ended up doing was taking a photo of the actual paper torn and cleaned up in Photoshop. It was so much more painless. Since papers are accessible to everyone, I recommend simply staging the paper the way you want it and photo/scan it in Photoshop.
The image you linked from CSS Tricks looks like a scanned photo to me, with artificial cast shadow.