请教div隐藏后又出现的问题?一下是aspx代码

<%@ Page language="c#" Codebehind="UploadFile.aspx.cs" AutoEventWireup="false" Inherits="CK.page.rk.UploadFile" %>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" >
<HTML>
  <HEAD>
<title>UploadFile</title>
<meta content="Microsoft Visual Studio .NET 7.1" name="GENERATOR">
<meta content="C#" name="CODE_LANGUAGE">
<meta content="JavaScript" name="vs_defaultClientScript">
<meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
<LINK href="/CK/Js/yh.css" type="text/css" rel="stylesheet"> <SCRIPT language="javascript">
function rb_uptypeChanged()
{

   if (document.getElementsByName("rb_uptype")[1].checked==true)
   {
       
       document.getElementById("div_jp").style.display="none";
      alert("1111");
       //document.getElementById("div_wj").style.display="block";
     
       
   }
    if (document.getElementsByName("rb_uptype")[2].checked==true)
    {
     
      
     // document.getElementById("div_wj").style.display="block";
      // document.getElementById("div_jp").style.display="none";
   }
    
          
}
</SCRIPT>
</HEAD>
<body class="bodyBg">
<form id="Form1" method="post" runat="server">
<table width="300" border="1" id="Table1">
<tr>
<td class="css_tr_gray1"><asp:radiobuttonlist id="rb_uptype" runat="server" AutoPostBack="True" RepeatDirection="Horizontal"
Font-Size="12px">
<asp:ListItem Value="wj" Selected="True">aaaa</asp:ListItem>
<asp:ListItem Value="jp">bbbb</asp:ListItem>
</asp:radiobuttonlist></td>
</tr>
<tr>
<td class="css_tr_gray1"><FONT face="宋体">cccc</FONT>
<asp:label id="lab_no" runat="server"></asp:label><FONT face="宋体">ddddd
<asp:label id="lab_detid" runat="server"></asp:label></FONT></td>
</tr>
</table>
<div id="div_wj" runat="server">
<table width="300" border="1" id="Table2">
<tr>
<td class="css_tr_gray1"><INPUT id="inputFile" type="file" name="inputFile" runat="server"></td>
<td class="css_tr_body1"><asp:button id="btn_up" runat="server" Text="ok"></asp:button></td>
</tr>
</table>
</div>
<div id="div_jp" runat="server">
<table width="300" border="1" id="Table3">
<tr>
<td class="css_tr_gray1">
<asp:TextBox id="txt_sno" runat="server"></asp:TextBox>
<td class="css_tr_body1">
<asp:Button id="Button1" runat="server" Text="Button"></asp:Button></td>
</tr>
</table>
</div>
</TABLE></form>
</body>
</HTML>