矩形

#square {width: 100px;height: 100px;background: red;}



圆形

#circle {width: 100px;height: 100px;background: red;
-moz-border-radius: 50px;
-webkit-border-radius: 50px;
border-radius: 50px;
}

椭圆

#oval {width: 200px;height: 100px;background: red;
-moz-border-radius: 100px / 50px;
-webkit-border-radius: 100px / 50px;
border-radius: 100px / 50px;
}

原文url:http://css-tricks.com/examples/ShapesOfCSS/#