<script type="text/javascript" src="http://www.dillerdesign.com/experiment/DD_roundies/DD_roundies_0.0.2a-min.js"></script>
<script type="text/javascript">
/* IE only */
DD_roundies.addRule('.roundify', '10px');

/* varying radii, IE only */
DD_roundies.addRule('.something_else', '10px 4px');

/* varying radii, "all" browsers */
DD_roundies.addRule('.yet_another', '5px', true);
</script>

http://www.nealgrosskopf.com/tech/thread.asp?pid=30

Find out how to do rounded corners in CSS. A new method has recently come out that makes it extremely easy to implement.

CSS Rounded Corners In Internet Explorer, Firefox & Safari Using Border Radius

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