Gracias a http://www.albin.net/CSS/roundedCorners/ por compartir esto

XHTML:
/ver en url albin.net
CSS:
.roundedCornerSpacer {
margin: 0px; padding: 0px; border: 0px;
clear: both;
font-size: 1px; line-height: 1px;
}
/* In the CSS below, the numbers used are the following:
1px: the width of the border
3px: a fudge factor needed for IE5/win (see below)
4px: the width of the border (1px) plus the 3px IE5/win fudge factor
14px: the width or height of the border image
*/
.borderTL, .borderTR, .borderBL, .borderBR {
width: 14px; height: 14px;
padding: 0px; border: 0px;
z-index: 99;
}
.borderTL, .borderBL { float: left; clear: both; }
.borderTR, .borderBR { float: right; clear: right; }
.borderTL { margin: -1px 0px 0px -1px; }
.borderTR { margin: -1px -1px 0px 0px; }
.borderBL { margin: -14px 0px 0px 0px; }
.borderBR { margin: -14px 0px 0px 0px; }
/* IE5-5.5/win needs the border scooted to the left or right by an
additional 3px! Why? */
.borderTL {
margin-left: -4px;
margin-left: -1px;
}
html>body .borderTL {
margin-left: -1px;
}
.borderTR {
margin-right: -4px;
margin-right: -1px;
}
html>body .borderTR {
margin-right: -1px;
}
.borderBL {
margin-left: -3px;
margin-left: 0px;
}
html>body .borderBL {
margin-left: 0px;
}
.borderBR {
margin-right: -3px;
margin-right: 0px;
}
html>body .borderBR {
margin-right: 0px;
}
/* To get around a known bug in IE5/win, apply the
border (no margin, padding or positioning) to the
content class and apply whatever positioning you
want to the contentWrapper class. */
.content {
margin: 0px;
padding: 0px;
border: 1px solid #00000;
}
.contentWrapper {
/* position this div however you want, but
keep its padding and border at zero */
padding: 0px;
border: 0px;
}