title: Disappearance of items from contentplaceholder on item click
body: <p>i am creating a master page in which there are two ContentPlaceHolders. ContentPlaceHolders1 is for the menu in which there are hyperlinks and in the other ContentPlaceHolders which is ContentPlaceHolders3, there the selected hyperlink will open its page. the problem is that the menu at the left apperars but when i click one of the hyperlink from it the page opens in ContentPlaceHolders3 but ther whole menu from ContentPlaceHolders1 disappears. picture.aspx and sample.aspx are the pages which are to be opened in ContentPlaceHolder3.</p>
  
  <p>here is the code for different pages:</p>
  
  <p>admin_panel.master:</p>
  
  <pre><code>&lt;%@ Master Language="C#" AutoEventWireup="true" CodeFile="admin_panel.master.cs" Inherits="admin_panel" %&gt;
  
  &lt;!DOCTYPE html&gt;
  
  &lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
  &lt;head runat="server"&gt;
      &lt;title&gt;&lt;/title&gt;
  
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;form id="form1" runat="server"&gt;
  
          &lt;table style="font-family: Arial"&gt;
              &lt;tr&gt;
                  &lt;td colspan="2" style="width: 800px; height: 80px; background-color: #3399FF; text-align: center"&gt;
                      &lt;h1&gt;WebSite Header&lt;/h1&gt;
                  &lt;/td&gt;
              &lt;/tr&gt;
              &lt;tr&gt;
                  &lt;td style="height: 500px; background-color: #66FFFF; width: 150px"&gt;
                      &lt;asp:ContentPlaceHolder ID="ContentPlaceHolder1" runat="server"&gt;
  
              &lt;/asp:ContentPlaceHolder&gt;
                  &lt;/td&gt;
                  &lt;td style="height: 500px; background-color: #9999FF; width: 650px"&gt;
                      &lt;h3&gt;Content&lt;/h3&gt;
                      &lt;div&gt;
                          &lt;asp:ContentPlaceHolder ID="ContentPlaceHolder3" runat="server"&gt;
                          &lt;/asp:ContentPlaceHolder&gt;
                      &lt;/div&gt;
                  &lt;/td&gt;
              &lt;/tr&gt;
  
          &lt;/table&gt;    
  &lt;/form&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>pictures.aspx:</p>
  
  <pre><code>    &lt;%@ Page Language="C#" EnableEventValidation="false" AutoEventWireup="true" CodeFile="pictures.aspx.cs" Inherits="pictures" MasterPageFile="~/admin_panel.master"%&gt;
  
  
          &lt;asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder3" Runat="Server"&gt;
  
              &lt;asp:Image ID="Image1" runat="server" Height="200px" /&gt;
              &lt;asp:Image ID="Image2" runat="server" Height="200px" /&gt;
              &lt;asp:Image ID="Image3" runat="server" Height="200px" /&gt;&lt;br /&gt;
              &lt;asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" /&gt;
  
          &lt;/asp:Content&gt;
  </code></pre>
  
  <p>sample:</p>
  
  <pre><code>&lt;%@ Page Language="C#" AutoEventWireup="true" CodeFile="sample.aspx.cs" Inherits="sample"  MasterPageFile="~/admin_panel.master"%&gt;
  
      &lt;asp:Content ID="nil" ContentPlaceHolderID="ContentPlaceHolder3" runat="server"&gt;
  
          &lt;div&gt;
          &lt;asp:Button ID="Button1" runat="server" Text="Button" OnClick="Button1_Click" style="height: 26px" /&gt;
      &lt;/div&gt;
  
      &lt;/asp:Content&gt;
  </code></pre>
  
  <p>admin.aspx:</p>
  
  <pre><code>&lt;%@ Page Title="" Language="C#" MasterPageFile="~/admin_panel.master" AutoEventWireup="true" CodeFile="admin.aspx.cs" Inherits="admin" %&gt;
  
  
  &lt;asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server" &gt;
      &lt;asp:HyperLink ID="HyperLink1" NavigateUrl="~/pictures.aspx" runat="server"&gt;Click Me&lt;/asp:HyperLink&gt;&lt;br /&gt;
      &lt;asp:HyperLink ID="HyperLink2" NavigateUrl="~/sample.aspx" runat="server"&gt;Click Me 2...&lt;/asp:HyperLink&gt;
  &lt;/asp:Content&gt;
  </code></pre>