为什么我写的没效果，看着老师的写的啊。
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>无标题文档</title>
<style>
*{margin:0;padding:0;}
#div1{
width:200px;
height:200px;
background:red;
filter:alpha(opacity:30);
opacity:0.3;
}
<script type="text/javascript">
window.onload=function(){
var oDiv = document.getElementById("div1");
oDiv.onmouseover=function(){
startMove(100);
};
oDiv.onmouseout=function(){
startMove(30);
}
};
var timer=null;
function startMove(iTarget){
var oDiv=document.getElementById("div1");
clearInterval(timer);
timer=setInterval(function(){
var speed = 0;
if(alpha > iTarget){
speed = -10;
}else{
speed=10;
}
if(alpha == iTarget){
clearInterval(timer);
}else{
alpha+=speed;
oDiv.style.filter='alpha(opacity:'+alpha+')';
oDiv.style.opacity=alpha/100;
}
},30)
}
</script>
</style>
</head>
<body>
<div id="div1"></div>
</body>
</html>
