drawing a circle with css

1#circle {
2  width: 100px;
3  height: 100px;
4  background: red;
5  border-radius: 50%
6}
7

1<div id="circle">
2</div>
3
4#circle {
5    width: 100px;
6    height: 100px;
7    background: red;
8    border-radius: 50%
9}

1#it is the border-radius:50; that makes the circle.
2.MyCircle{
3  width:100px;
4  height:100px;
5  background-color:blue;
6  border-radius:50px;
7}