Problem with table row visibility

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C#

ASP.NET

C#4.0

Hi all,
I am developing an ASP.net application with c# in VS2010. My web page contains a dropdownlist with 4 options and on select of each item it shows different items as below. Please refer to the code below.

<asp:Label ID="Label1" runat="server" Text="Select any filter">
<asp:DropDownList ID="ddlfilter" runat="server" AppendDataBoundItems="True" CssClass="TextBox" onchange="return changefilter()">
     <asp:ListItem>Select a filter
     <asp:ListItem>Date Range
     <asp:ListItem>Paralegal Name<small></small>
     <asp:ListItem>Group Name

The rows to display:-

<tr id="1" style="display: none">
   <td>
      <asp:TextBox ID="txtStartDate" runat="server">
      <asp:TextBox ID="txtEndDate" runat="server" >
   </td>                                 
 </tr>

 <tr id="2" style="display: none><br mode=" hold=" />
   <td><br mode=" ddlparalegalname=" runat=" server=" AppendDataBoundItems=" true="<br mode=" employeename=" DataValueField=" employeeid=" ><br mode=" 3=" style=" none="> <br mode=" txtgroupname=" runat=" block=";<br mode=">
</tr>