For Firefox

/* To adjust all corners */

-moz-border-radius: 10px;

/* To adjust individual corners */

-moz-border-radius-topleft: 10px;
-moz-border-radius-topright: 10px;
-moz-border-radius-bottomleft: 10px;
-moz-border-radius-bottomright: 10px;

For Safari & Chrome

/* To adjust all corners */

-webkit-border-radius: 10px;

/* To adjust individual corners */

-webkit-border-top-left-radius: 10px;
-webkit-border-top-right-radius: 10px;
-webkit-border-bottom-left-radius: 10px;
-webkit-border-bottom-right-radius: 10px;

For Internet Explorer 7 & 8.
Click this IE Rounded Corner Hack - using css border-radius, cool!