Makes use of different borders, border radius and a perpetual spin animation.
.circle {
width: 80px;
height: 80px;
border-radius: 50px;
-webkit-box-sizing: border-box;
border: solid 8px rgba(255, 255, 255, 0.2);
border-top-color: #FFF;
-webkit-animation: spin 1s infinite linear;
}
@-webkit-keyframes spin {
100% {
-webkit-transform: rotate(360deg);
}
}