.circle{
  width:40px;
  height:40px;
  border-radius:150px;
  border:10px solid #fff;
  border-top-color:rgba(0,0,0,0.3);
  box-sizing:border-box;
  position:absolute;
  left:50%;
  margin-top:-20px;
  margin-left:100px;
  animation:circle 1s linear infinite;
  -webkit-animation:circle 1s linear infinite;
}
@keyframes circle{
  0%{transform:rotate(0deg)}
  100%{transform:rotate(360deg)}
}
@-webkit-keyframes circle{
  0%{-webkit-transform:rotate(0deg)}
  100%{-webkit-transform:rotate(360deg)}
}