If you set the CssClass property on the Panel that is referenced by the CollapsibePanel's TargetControlID, two div elements with the same CssClass will be created. Making it impossible to apply common styles to the Panel (Borders, Padding, Margin, you get the picture :)
For example:
<div style="overflow: hidden; height: 31px; width: 112px;" id="ctl00_Navigation_PanMenuOperating Figures" class="MenuPanel">
<div style="height: auto;" id="" class="MenuPanel">
The first div is my Panel, the second is created by the CollapsiblePanel.
An easy workaround is to add another Panel inside and apply the CssClass to it, but its annoying.
Comments: We tested this control in all modern browsers (including Firefox) and did not detect the described problem in the current v15.1 version of Ajax Control Toolkit.
For example:
<div style="overflow: hidden; height: 31px; width: 112px;" id="ctl00_Navigation_PanMenuOperating Figures" class="MenuPanel">
<div style="height: auto;" id="" class="MenuPanel">
The first div is my Panel, the second is created by the CollapsiblePanel.
An easy workaround is to add another Panel inside and apply the CssClass to it, but its annoying.
Comments: We tested this control in all modern browsers (including Firefox) and did not detect the described problem in the current v15.1 version of Ajax Control Toolkit.