Even though CSS3 has brought a lot to the table in regards to drop shadow effects, there are still plenty of reasons to use image alternatives. The drop shadows generated by CSS3 are relatively uniform, and don’t deviate much past size and transparency. In some cases, you might want to give a page some extra depth.
I ran into a similar situation in a recent client project, and decided to use a recent trend of warping drop shadows to help add some extra excitement to the page. You might have seen similar effects in other tutorials involving deleting a circular section, but this method will keep the edges from being too sharp. It also allows you to work with non-rectangular shapes because all points are editable in the warp tool’s grid.
Read the full tutorial @ BuildInternet.com