求助斑竹，为什么显示不出图片来了？
<script language="javascript">var yzm=Math.floor((Math.random()*10000))
a=Math.floor(yzm/1000);
b=Math.floor(yzm/100)-a*10;
c=Math.floor(yzm/10)-a*100-b*10;
d=Math.floor(yzm)-a*1000-b*100-c*10
function chuan()
{
var c=document.form1.yzm1.value
if(c!=yzm)
{
alert("验证码错误！");
document.form1.yzm1.value="";
return false
}
}
</script>
</head>
<body>
<form name="form1" method="post" action="http://www.baidu.com" onSubmit="return chuan()">
验证码：<input type="text" name="yzm1" /><img src="image/<script>document.write(a)</script>.jpg" /><img src="image/<script>document.write(b)</script>.jpg" /><img src="image/<script>document.write(c)</script>.jpg" /><img src="image/<script>document.write(d)</script>.jpg "/>
<br />
<input type="submit" name="submit1" value="提交" />
</form>
