ovo provereno radi. dajem ti samo kao primer. sorry sto je malo nepregledno, kopirao sam iz svog projekta
<ajaxToolkit:Accordion ID="accNav" runat="server" SelectedIndex="0"
HeaderCssClass="accordionHeader" ContentCssClass="AccordionContent" FadeTransitions="true"
FramesPerSecond="40" TransitionDuration="250" AutoSize="None" >
<Panes>
<ajaxToolkit:AccordionPane ID="AccordionPane1" runat="server">
<Header>
<asp:Panel ID="pnlSalesActivity" runat="server" CssClass="AccordionHeader">
Sales Activity
</asp:Panel>
</Header>
<Content>
<uc2:FCSalesActivity ID="FCSalesActivity2" runat="server" OnLeadClicked="FCSalesActivity2_LeadClicked" OnTaskClicked="FCSalesActivity2_TaskClicked" OnChecklistClicked="FCSalesActivity2_ChecklistClic ked" />
</Content>
</ajaxToolkit:AccordionPane>
<ajaxToolkit:AccordionPane ID="AccordionPane2" runat="server">
<Header>
<asp:Panel ID="Panel1" runat="server" CssClass="AccordionHeader">
Client Pipeline Activity
</asp:Panel>
</Header>
<Content>
<uc3:FCPipelineActivity ID="FCPipelineActivity2" runat="server" />
</Content>
</ajaxToolkit:AccordionPane>
<ajaxToolkit:AccordionPane ID="AccordionPane3" runat="server">
<Header>
<asp:Panel ID="Panel2" runat="server" CssClass="AccordionHeader">
Business Analysis
</asp:Panel>
</Header>
<Content>
<uc4:FCBusinessAnalysis ID="FCBusinessAnalysis2" runat="server" />
</Content>
</ajaxToolkit:AccordionPane>
<ajaxToolkit:AccordionPane ID="AccordionPane4" runat="server">
<Header>
<asp:Panel ID="Panel3" runat="server" CssClass="AccordionHeader">
Search
</asp:Panel>
</Header>
<Content>
<uc5:SearchClientCss ID="SearchClientCss2" runat="server" ValidationGroup="Search2" OnSearchClicked="SearchClientCss_SearchClicked" />
</Content>
</ajaxToolkit:AccordionPane>
</Panes>
</ajaxToolkit:Accordion>