Please don't use this version of the effect. I've seen in on a couple of websites, and it seriously pains me to see it.

Because the "page" doesn't actually "curl", it looks more like background has been pushed down in places.

I’m guessing they used it on a large element. Something like this is definitely meant for a sub-300px element, where the eye would get tricked into thinking there was a page curl.

Great one, quite decent.