Tab Container not visible

I am trying to add a TabContainer to a blank page but it will not show.  There are no error messages but nothing will show on the page.

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %><asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager><asp:TabContainer ID="TabContainer1" runat="server" ActiveTabIndex="0" 

                width="500px"><asp:TabPanel runat="server" ID="TabPanel1"> <HeaderTemplate><div class="tabsize">Contact Us</div></HeaderTemplate>          <ContentTemplate>             

I even tried a TabContainer from a working page but it would not display either.