怎么样才能在IE上显示？
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
</head>
<body>
<div class="ddiv">
<dl onmouseover="showbig(event);" onmouseout="normal(event);">
<dt>
<dd><img id="a001" src="img/微笑.jpg" style="width: 300px;" /></dd>
<dd><img id="a002" src="img/笑.jpg" style="width: 300px;" /></dd>
<dd><img id="a003" src="img/大笑.jpg" style="width: 300px;" /></dd>
</dt>
</dl>
</div>
<script type="text/javascript">
function showbig(event){
var a1=event.target.id;
var a1=document.getElementById(a1);
a1.style.width="400px";
}
function normal(event){
var a1=event.target.id;
var a1=document.getElementById(a1);
a1.style.width="300px";
}
</script>
</body>
</html>
