Microsoft Internet Explorer 9 Arrives: 10 Reasons to Use It

http://www.eweek.com/c/a/Enterprise-Applications/Microsoft-Internet-Explorer-9-Arrives-10-Reasons-to-Use-It-851132/

CSS3 Rounded corners in IE9

The border-radius properties enable you to curve border corners by essentially “replacing” the hard corners with a quarter-ellipse and specifying the radii of each ellipse. The properties consist of the following:

• border-radius (The value given will specify the radius for all four corners of a box.)
• border-bottom-left-radius
• border-bottom-right-radius
• border-top-left-radius
• border-top-right-radius

For example, take a look at the following markup:

border-radius: 100px 66.66px 200px 50px;
border: 10px blue double;
padding: 24px;
width: 400px;height: 125px;

Reference:
http://msdn.microsoft.com/en-us/ie/ff468705#_CSS3_BG_Borders