xxxxxxxxxx
.circle {
width: 100px;
height: 100px;
border-radius: 50%; /* setting border radius to 50% of the element's dimensions to create a circle */
background-color: #dddddd;
}
xxxxxxxxxx
.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>
xxxxxxxxxx
.circle {
width: 100px;
height: 100px;
border-radius: 50%;
border: 2px solid black;
}