<html>
<head>
<style type="text/css">
body{
background-color: green;
}
.circle{
margin:0 auto;
margin-top:150px;
background-color: gray;
width: 10em;
height: 10em;
border-radius: 50%;
border: 1.1em solid rgba(255,255,255,0.2);
border-left-color:#fff;
-webkit-animation: load 1.1s infinite linear;
}
@-webkit-keyframes load{
from{
transform:rotate(0deg);
}
to{
transform:rotate(360deg);
}
}
</style>
</head>
<body>
<div class="circle">
</div>
</body>
</html>
原文：http://www.cnblogs.com/chengshuiqiang/p/4740932.html