rounded edges

[Noodle7]

Hi there

How do you create rounded box ( which is opaque - can see background image) holds the nav bar, #topleft .textblock {
text-align: left;
position: absolute;
width: 230px;
height: auto;
top: 15px;
left: 14px;
opacity: 0.5;
filter: alpha(opacity=50);
-moz-opacity: 0.50;
-khtml-opacity: 0.5;
background: white;
font-family: Arial, Helvetica, sans-serif;
font-size: 13px;
color: #000000;
font-weight: bold;
letter-spacing: 2px;
line-height: 22px;
padding: 0px;
align: left;} this is code but I know want to create rounded edges any ideas?

[Kravvitz]

Spanky Corners (http://tools.sitepoint.com/spanky/)
http://www.alistapart.com/articles/slidingdoors/
http://www.alistapart.com/articles/slidingdoors2/
http://www.alistapart.com/articles/customcorners/
http://www.alistapart.com/articles/customcorners2/
http://www.cssplay.co.uk/boxes/curves.html