opacity与filter：olpha（opacity）的兼容性，我的ie9兼容opacity，设置filter：olpha（opacity）是否有必要
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
body{margin: 0;padding: 0;}
#div1{
background:red;
width: 400px;
height: 400px;
filter: alpha(opacity:30);
opacity: 0.3;
}
</style>
</head>
<body>
<!-- Javascript -->
<script type="text/javascript">
window.onload = function(){
var oDiv = document.getElementById('div1');
oDiv.onmouseover = function(){
starMove(0.1,1)
}
oDiv.onmouseout = function(){
starMove(-0.1,0.3)
}
}
var timer = null;
var opacity = 0.3;
function starMove(speed,ita){
clearInterval(timer);
var oDiv = document.getElementById('div1');
timer=setInterval(function(){
if (oDiv.style.opacity==ita) {
clearInterval(timer);
}
else{
opacity = opacity + speed;
oDiv.style.opacity = opacity + speed;
}
},100)
}
</script>
<!-- html -->
<div id="div1"></div>
</body>
</html>以上代码没有设置filter：alpha（opacity）但是兼容自带的ie9，百度有人说opacity通用，那么opacity的兼容性到底如何；是否只是兼容高版本ie还是真的通用，以及filter：alpha（opacity）的设置是否有必要
