We have to creat a class like below
<style>

.roundc{

border:2px solid #ff0000;

border-radius:25px;

background:#dddddd;

width:300px;

-moz-border-radius:25px; /* Firefox */

-webkit-border-radius:25px; /* Chrome and Safari */

-o-border-radius:25px; /* Opera */

}

</style>

and we have to add this class where we want the round corner like in below div

<div class=”roundc” > this is the round corner by css3 </div>