Hi, this is my issue:

I have a master page in C#, where I have this code:

<div style="width: 30%;height: 500px;float:left">
        <asp:ContentPlaceHolder ID="cphMenu" runat="server">
        </asp:ContentPlaceHolder> 
    </div>


    <div style="width: 65%;height: 500px; float:right">
       <asp:ContentPlaceHolder ID="cphMain" runat="server">            
       </asp:ContentPlaceHolder>        
    </div>

As you can see, I have two ContentPlaceHolders, the first one is the left menu (cphMenu), and the second one is the page itself. So, I want to click an item from the menu (the menu is a treeview) and load that specific page on the second contentplaceholder (cphMain).

How can I get that behaviour??

Thanks in advance.