An accordion allows you to display formatted text, images, and Web pages in an organized list of expandable panes that are revealed one pane at a time. Users simply select a pane to expand it and view the specified information while the other panes are collapsed, automatically organizing your user interface and optimizing the screen real estate.
C1AccordionExtender Markup
The following markup creates a C1AccordionExtender control. Set the TargetControlID property to attach the extender to a control.
<cc1:C1AccordionExtender ID="Panel1_C1AccordionExtender" runat="server"
TargetControlID="Panel1">
</cc1:C1AccordionExtender>