Answer 1

set width= height and
border radius 100%
div{
background:#000;
width:100px;
height:100px;
color:#FFF;
border-radius:100%;
}

Answer 2

Prashanth Kumar
border-radius:50%; is sufficient...

Answer 3

Bob_Li yeah ...

Answer 4

Add div and set width and height with colour except white then set border-radius 50% or100%

Answer 5

By using border-radius: 50%; you can get it;
for example:
div {
width: 50px;
height: 50px;
background: red;
border-radius: 50%;
}
make sure to use same value for "width" and "height", otherwise you'll get an ellipse instead of a circle.