AJAX :: Client PC Can't Pop Calendar Extender

I have some aspx pages where I was using a date picker. I changed the date picker with AJAX calendarextender which I can pop by clicking on the associated textbox when I am viewing this page on the server itself. But on the client PC I can't pop the calendar. This textbox and calendarextender are created in a gridview.

<asp:GridView id="EmpList" runat="server" Caption="Employee Personal Data"
AutoGenerateColumns="False" DataKeyNames="RECID, ENumber"
AutoGenerateEditButton="True"
DataSourceID="EmpData"
allowsorting="true">
<columns>
<asp:BoundField HeaderText="E/Number" DataField="ENumber" sortexpression="ENumber" readonly="True"/>
<asp:BoundField HeaderText="E/Name" DataField="EName" sortexpression="EName"/>
<asp:TemplateField HeaderText="Date Joined" sortexpression="DOJ">
<ItemTemplate><asp:Label ID="lblDOJ" Runat="Server" Text='<%# Eval("DOJ", "{0:d}") %>' /></ItemTemplate>
<EditItemTemplate>
<asp:TextBox ID="txtDOJ" runat="server" Columns="8" text='<%# Eval("DOJ", "{0:d}") %>' ReadOnly="True"></asp:TextBox>
<asp:CalendarExtender ID="txtDOJEx" runat="server" TargetControlID="txtDOJ"></asp:CalendarExtender>
</EditItemTemplate>
</asp:TemplateField>
</columns>
</asp:GridView>
</code>

Is there anything that I am missing?