border radius on one corner code example

Example 1: css circle border

.circle {
    background-color:#fff;
    border:1px solid red;    
    height:100px;
    border-radius:50%;
    -moz-border-radius:50%;
    -webkit-border-radius:50%;
    width:100px;
}
<div class="circle"></div>

Example 2: css rounded corners at top only

border-radius: 10px     10px      0           0;
            // top-left top-right bottom-right bottom-left.