1
2 #circle {
3 width: 100px;
4 height: 100px;
5 background: red;
6 border-radius: 50%
7 }
8
1.circle {
2 background-color:#fff;
3 border:1px solid red;
4 height:100px;
5 border-radius:50%;
6 -moz-border-radius:50%;
7 -webkit-border-radius:50%;
8 width:100px;
9}
10<div class="circle"></div>