<div>
is done using border-radius
property.border-radius:1px;
means rounded corners for all 4 corners with 1 pixel radius.border-radius:1px 2px 3px 4px;
means 1 pixel radius rounded corner for top - right, 2 pixels radius rounded corner for bottom - right, 3 pixels radius rounded corner for bottom - left, and 4 pixels radius rounded corner for top - left.