AJAX calender control

Question

Hi Friends...
 
I have AJAX calender control in my application.
 
But i am not able to select the day before from current date.
 
Only able to select after the current date.
 
What can i Do.
 

<asp:Label ID="lblstartdate" Text="Start Date" CssClass="lbl" runat="server"></asp:Label>                            <AjaxToolkit:ToolkitScriptManager ID="ToolkitScriptManager1"  runat="server">                            </AjaxToolkit:ToolkitScriptManager>                            <asp:TextBox ID="txtstartdate" CssClass="txtbox" runat="server"></asp:TextBox>                             <ajaxtoolkit:calendarextender  runat="server" ID="calExtender2"                              PopupButtonID="btnDate3" TargetControlID="txtstartdate" Format="MMMM d, yy" />                            <asp:ImageButton ID="btnDate3" ImageUrl="~/images/CalendarIcon.jpg" Width="20px"                                runat="server" />