Border-radius
Recently i discovered the nice new CSS3 border-radius. Currently it only works in Firefox and safari but it is awesome. Pair that up with a background image and the corners become rounded just as you intended but you no longer need to make images for the top and bottom.
If viewing in firefox, you can view an example of this at www.williamdeerfield.com
For more information on border-radius tag: http://www.css3.info/preview/rounded-border/
