Just got back from the ghost town (ACT forum)

The wind is howling down the deserted street, rolling tumbleweeds along helter-skelter, over in the Ajax Control Toolkit forum, so:

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I am trying to use CollapsiblePanelExtender. I've got two panels to work with it, one named PnlTitle that, from the user's perspective, cause the panel below it (PnlContent) to toggle between being expanded and collapsed.

I've set the properties of the CollapsiblePanelExtender to what seems logical:

<ajaxToolkit:CollapsiblePanelExtender ID="CollapsiblePanelExtender1" runat="server" TargetControlID="PnlContent" ExpandControlID="PnlTitle"
    CollapseControlID="PnlTitle" TextLabelID="Label1"
    CollapsedText="Show Details (...)" ExpandedText="Hide Details (...)"
    I ...