how to make a round corner in css

1/* Set rounded corners with border-radius property */
2
3.class {
4  border-radius: 4px;
5}
6
7.circle {
8  border-radius: 50%;
9}

1#roundCornerID {
2    border-radius: 30%;
3    width: 200px;
4    height: 150px;   
5}

1/* I find it best to use pixels*/
2    border-radius: 5px;
3
4/* Percents don't work well with elements that aren't square*/
5    border-radius: 10%;