Source

<asp:Panel ID="Panel1" DefaultButton="Button1" runat="server">      
  <asp:TextBox ID="TextBox1" Width="180px" runat="server"></asp:TextBox>
  <cc1:TextBoxWatermarkExtender ID="TextBox1_TextBoxWatermarkExtender" runat="server"
  Enabled="True" WatermarkCssClass="watermarked" TargetControlID="TextBox1" 
  WatermarkText="Type text and press enter">
  </cc1:TextBoxWatermarkExtender>
  <asp:Button ID="Button1" runat="server" Text="Button1" onclick="Button1_Click" />
  <asp:Label ID="Label1" runat="server" Text=""></asp:Label>    
</asp:Panel>

<asp:Panel ID="Panel2" DefaultButton="Button2" runat="server">  
  <asp:TextBox ID="TextBox2" Width="180px" runat="server"></asp:TextBox>
  <cc1:TextBoxWatermarkExtender ID="TextBox2_TextBoxWatermarkExtender" runat="server" 
    Enabled="True" WatermarkCssClass="watermarked" TargetControlID="TextBox2" 
    WatermarkText="Type text and press enter">
  </cc1:TextBoxWatermarkExtender>
  <asp:Button ID="Button2" onclick="Button2_Click" runat="server" Text="Button2" />
  <asp:Label ID="Label2" runat="server" Text=""></asp:Label>
</asp:Panel>