javascript文本框赋值问题

实现提交后将密码赋值到另一个textbox中，并显示，我写的代码如下，请高手帮忙找错误
<head runat="server">
    <title>测试</title>
</head><script language="javascript">
    function pwd()
    {
        var pawd=document.getElementById("TextBox1").value;
        document.getElementById("TextBox2").value=pawd;
        alert("ok");
    }
</script><body>
    <form id="form1" runat="server">
    <div>
    
        <asp:TextBox ID="TextBox1" runat="server" TextMode="Password"></asp:TextBox>
    
    </div>
    <p>
        <asp:TextBox ID="TextBox2" runat="server" Visible="False" />
    </p>
    <p>
        <asp:Button ID="Button1" runat="server" Text="Button" OnClick="pwd()"></asp:Button>
    </p>
    </form>
</body>