我的javascript代码怎么不起作用啊?请高人指点。

在下面的代码中不管有没有输入用户名、密码，按登陆都会提交表单，login函数没起作用，这是怎么回事啊。请指教，谢谢
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<script language="javascript">
<!--
function login()
{
var username = document.form1.username.value;
var password = document.form1.password.value;
if ( username == "")
{
alert ( "请输入用户名");
return false;
}
if ( password == "" )
{
alert ( "请输入密码");
return false;
}
return true;
}
-->
</script>


<meta http-equiv="Content-Type" content="text/html; charset=gb2312">
<title>交易监控系统</title>
</head>

<body>


<div align="center">
<p><FONT face=隶书 size=6><img src="resource/spb-star2.gif" width="60" height="49"><img src="resource/logo.png" width="130" height="35">交易监控系统</FONT></p>

<script language="JavaScript">
today= new Date()
document.write("<font color=black>",today.getYear(),"年",today.getMonth()+1,
"月",today.getDate(),"日");
</script>

<form name="form1" method="post" action="Login" onsubmit="return login()">
<p> </p>
<p class="style1"> </p>
<table width="23%" border="1" cellspacing="0">
<tr>
<td width="38%" height="45"><div align="center" class="style5">用户名</div></td>
<td width="62%"><div align="center">
<input name="username" type="text" id="username" size="9" maxlength="8">
</div></td>
</tr>
<tr>
<td height="44"><div align="center" class="style5">密 码</div></td>
<td><div align="center">
<input name="password" type="password" id="password" size="8" maxlength="8">
</div></td>
</tr>
</table>
<p>
<input name="login" type="submit" id="login" value="登陆">
<input type="reset" name="reset" value="重置">
</p>
<p> </p>
<p>  </p>

</form>
</div>
</body>
</html>