javaScript中的alert()不起作用

<script language="javaScript">
function validate(f){
if(!(/^\w{5,15}$/.test(f.userId.value))){
alert("用户id必须是5~15为");
f.userId.focus();
return false;
}
if(!(/^\w{5,15}$/.test(f.passWord.value))){
alert("用户密码必须是5~15为");
f.passWord.focus();
return false;
}
return true;
}
</script>
<from action="check.jsp" method="post" onSubmit="return validate(this)">
<table border="0">
<tr>
<td colspan="2"><h1>用户登录程序</h1></td>
</tr>
<tr>
<td> 用户id：</td>
<td><input type="text" name="userId" size="20"></td>
</tr>
<tr>
<td> 密 码：</td>
<td><input type="password" name="passWord" size="21"> </td>
</tr>
<tr>
<td >
<input type="submit" value="登录">
<input type="reset" value="重置">
</td>
</tr>
</table>
</form>