代码如下：
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>CSS3圆圈动画放大缩小循环动画效果</title>
<style>
.dot {
margin:150px auto;
width:200px;
height:200px;
background-color:#E3E3E3;
border-radius: 50%;
box-shadow: 0 0 10px rgba(0,0,0,.3) inset;
-webkit-animation-name:'ripple';/*动画属性名，也就是我们前面keyframes定义的动画名*/
-webkit-animation-duration: 2s;/*动画持续时间*/
-webkit-animation-timing-function: ease; /*动画频率，和transition-timing-function是一样的*/
-webkit-animation-delay: 0s;/*动画延迟时间*/
-webkit-animation-iteration-count: infinite;/*定义循环资料，infinite为无限次*/
-webkit-animation-direction: alternate;/*定义动画方式*/
}
@keyframes ripple {
0% {
opacity:0.35;
width:190px;
height:190px;
}
100% {
opacity: 0.2;
width:250px;
height:250px;
}
}
</style>
</head>
<body>
<div class="dot"></div>
</body>
</html>