使用CSS3 box-shadow属性滚动延迟？

I added a box-shadow to a section of a page recently to give it the same shadow border effect that is seen on Mac OS X apps. It looked great, but I noticed that scrolling up and down on the page made it lag. I usually only see this on pages that have annoying background images and tons of images and embedded videos plastered all over ( to a section of a page rec