Måske fordi du ikke har fulgt opskriften 100 % ? :-)
Dette her producerer regnbuen på min skærm:
<%@ Page Language="VB" AutoEventWireup="false" CodeFile="TestTabCss.aspx.vb" Inherits="Helpdesk_TestTabCss" %>
<%@ Register Assembly="System.Web.Extensions, Version=1.0.61025.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35"
Namespace="System.Web.UI" TagPrefix="asp" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "
http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="
http://www.w3.org/1999/xhtml" >
<head runat="server">
<title>Untitled Page</title>
<style type="text/css">
.mytab .ajax__tab_header
{
background-color: brown;
}
.mytab .ajax__tab_outer
{
background-color: red;
}
.mytab .ajax__tab_inner
{
background-color: blue;
}
.mytab .ajax__tab_tab
{
background-color: yellow;
}
.mytab .ajax__tab_body
{
background-color: green;
}
.mytab .ajax__tab_hover
{
background-color: black;
}
.mytab .ajax__tab_active
{
background-color: red;
}
</style>
</head>
<body>
<form id="form1" runat="server">
<asp:ScriptManager ID="ScriptManager1" runat="server" />
<div>
<cc1:TabContainer ID="TabContainer1" runat="server" CssClass="mytab">
<cc1:TabPanel ID="TabPanel1" runat="server">
<ContentTemplate>aaaa
</ContentTemplate>
</cc1:TabPanel>
<cc1:TabPanel ID="TabPanel2" runat="server">
<ContentTemplate>bbbb</ContentTemplate>
</cc1:TabPanel>
</cc1:TabContainer>
</div>
</form>
</body>
</html>