CSS3 动画旋转怎么写？

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"> 
<title>CSS3 动画 旋转DEMO</title>
<style> 
div
{
    width:100px;
    height:100px;
    background:red;
    position:relative;
    animation-name:myfirst;
    animation-timing-function: linear;
    animation-duration:5s;
    animation-iteration-count:infinite; 
    animation-play-state: running;
}

@keyframes myfirst
{
    0%   {background:red; left:100px; top:100px;}
    100% {transform:rotate(360deg); left:100px; top:100px;}
}


</style>
</head>
<body>

<p><b>注意:</b> 该实例在 Internet Explorer 9 及更早 IE 版本是无效的。</p>

<div></div>

</body>
</html>