The Accordion is a web control that allows you to provide multiple panes and display them one at a time.It is like having several CollapsiblePanels where only one can be expanded at a time.

<ajaxToolkit:Accordion ID="MyAccordion" runat="server" SelectedIndex="0"
FadeTransitions="false" FramesPerSecond="40" TransitionDuration="250"
AutoSize="None" RequireOpenedPane="false" SuppressHeaderPostbacks="true">

<Panes>

<ajaxToolkit:AccordionPane ID="AccordionPane1" runat="server">

<Header><a href="">1. AccordionPane1</a></Header>

<Content>

Type your content here</Content>

</ajaxToolkit:AccordionPane>

<ajaxToolkit:AccordionPane ID="AccordionPane2" runat="server">

<Header><a href="">2. AccordionPane2</a></Header>

<Content>

content goes here

</Content>

</ajaxToolkit:AccordionPane>

</Panes>

</ajaxToolkit:Accordion>

Related posts:

1. Accordion Menu using JQuery
2. CollapsiblePanel
3. TextBoxWatermarkExtender
4. ValidatorCalloutExtender
5. Ajax Tabs