I saw an image as the 404 error in CSS Tricks, and I wondered how to create such an effect in Photoshop.
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.
i worked on the same thing ages ago, all you have to seriously work with selection tool when it comes to edges i did all this with the help of "richard carpentar" given tutorial,edit and play with the details when working and you'll get your output, check this out surely it will help....
something very same....
Hope this will help :)