<div id="round"></div>
#round {
    padding:10px; width:300px; height:50px;
    border: 5px solid #dedede;
    -moz-border-radius: 15px;      /* Gecko browsers */
    -webkit-border-radius: 15px;   /* Webkit browsers */
    border-radius:15px;            /* W3C syntax */
}

<div id="round"></div>  
#round {
    padding:10px; width:300px; height:50px;
    background:#FC9; 
    -moz-border-radius: 15px;
    -webkit-border-radius: 15px;
    border-radius:15px;
}

/* Gecko browsers */
-moz-border-radius: 5px; 
/* Webkit browsers */
-webkit-border-radius: 5px; 
/* W3C syntax - likely to be standard so use for future proofing */
border-radius:10px;

border-radius:5px 15px 20px 25px;

/* Gecko browsers */
-moz-border-radius-topleft: 20px;
-moz-border-radius-topright: 0;
-moz-border-radius-bottomleft: 0;
-moz-border-radius-bottomright: 20px;
 
/* Webkit browsers */
-webkit-border-top-left-radius: 20px;
-webkit-border-top-right-radius: 0;
-webkit-border-bottom-left-radius: 0;
-webkit-border-bottom-right-radius: 20px;
 
/* W3C syntax */
border-top-left-radius: 20px;
border-top-right-radius: 0;
border-bottom-right-radius: 0;
border-bottom-left-radius:  20px;