比較好的密碼確認

<script type="text/javascript">
     function atg()
     {
        var txt1=document.getElementById("txtSendMailpw").value;
        var txt2=document.getElementById("txtpwok").value;
        if(txt1.charAt(txt2.length-1)!=txt2.charAt(txt2.length-1))
        {
            document.getElementById("table1").style.display= "block";
        }
        else
        {
            if(txt2==txt1.substring(0,txt2.length))
            {
                document.getElementById("table1").style.display= "none";
            }
        }
     }
    </script>

 新密碼：<asp:TextBox ID="txtSendMailpw" runat="server" CssClass="textfield" TextMode="Password"
                                            Width="150px">000</asp:TextBox>

確認密碼：<asp:TextBox ID="txtpwok" runat="server" CssClass="textfield" TextMode="Password"
                                            Width="150px" οnkeyup="atg()">000</asp:TextBox>

<table id="table1" style="display: none;" align="center">
            <tr>
                <td>
                    <font style="color: Red">確認密碼輸入不正確</font></td>
            </tr>
        </table>