I like the look of rounded corners on various elements so I have been experimenting on a method of creating them with CSS. Conceptually, it's simply a matter of onion-skinning the layers so one slides over the other (see ALA: onion skinned drop shadows plus sliding doors of CSS).

For my example, I created 4 corner images which are positioned in divs that layer one atop the other. Semantically, the CSS needs work but the concept is there.