Here is a jsfiddle so you can see an example of this working.
HTML code:
<div class="circle"></div>
CSS code:
.circle {_x000D_
/*This creates a 1px solid red border around your element(div) */_x000D_
border:1px solid red;_x000D_
background-color: #FFFFFF;_x000D_
height: 100px;_x000D_
/* border-radius 50% will make it fully rounded. */_x000D_
border-radius: 50%;_x000D_
-moz-border-radius:50%;_x000D_
-webkit-border-radius: 50%;_x000D_
width: 100px;_x000D_
}
_x000D_
<div class='circle'></div>
_x000D_