css to modal

I can't get my css file to apply to this page. It pops up ok.

<%@ Page Language="VB" MasterPageFile="~/MasterPage.master" AutoEventWireup="false" CodeFile="Modal.aspx.vb" Inherits="test_Modal" title="Untitled

Page" %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>

<asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
    <asp:ScriptManager ID="ScriptManager1" runat="server">
    </asp:ScriptManager>
      <link href="../App_Themes/Theme1/test.css" rel="stylesheet" type="text/css" media="screen"/>

 <asp:UpdatePanel ID="UpdatePanel1" runat="server">
    <ContentTemplate>      
        <cc1:ModalPopupExtender ID="ModalPopupExtender1" runat="server" TargetControlID="LinkButton3" PopupControlID="Panel1"

CancelControlID="LinkButton2" Drag="true">
         </cc1:ModalPopupExtender>
         
        <asp:LinkButton ID="LinkButton3" runat="server">LinkButton</asp:LinkButton>
         
    <asp:PlaceHolder ID="PlaceHolder1" runat="server" >       
 
        <asp:Panel ID="Panel1" runat="server"  CssClass="modalPopup">
                <br />    
        <asp:UpdatePanel ID="UpdatePanel2" runat="server">  
            <ContentTemplate>
             <asp:TextBox ID="txtfirstname_1" runat="server"></asp:TextBox>
              <cc1:TextBoxWatermarkExtender ID="txtfirstname_TextBoxWatermarkExtender"
                    runat="server" Enabled="True" TargetControlID="txtfirstname_1"
                    WatermarkText="Firstname">
                </cc1:TextBoxWatermarkExtender>
         
        </ContentTemplate>
       
        </asp:UpdatePanel>
           
      <asp:LinkButton ID="LinkButton2" runat="server">Close</asp:LinkButton>  
  </asp:Panel>&nbsp;
  </asp:PlaceHolder>
 
    </ContentTemplate>
    </asp:UpdatePanel>
</asp:Content>


Test.css   file



body
{
   margin:0;
   padding:0;
   border:none;
}

    /*Modal Popup*/
.modalBackground
{
    background-color: #C0C0C0;
    -ms-filter: alpha(opacity=70);
    -ms-opacity: 0.7;
}

.modalPopup
{
    background-color: #FF0066;
    border-width: 1px;
    border-style: solid;
    border-color: Gray;
    padding: 3px;
    width: 870px;
    overflow: auto;
}