ExpandedImage and CollapsedImage not displaying when load

Hi there,
I have a page that has a CollapsiblePanel that has not text on it as of yet. When i set it up to display images in the following properties ExpandedImage="images/collapse_blue.jpg" CollapsedImage="images/expand_blue.jpg" nothing actually happens.
my question here is how do i get to display the text and the image on the header portion?
below is my code
Thanks,
Cohfl

<asp:Panel ID="PnlTitle" runat="server" CssClass="collapsePanelHeader"/>
                <asp:Panel ID="PnlContent" runat="server" CssClass="collapsePanel"/>
        
                <cc1:CollapsiblePanelExtender ID="CollapsiblePanelExtender1" 
            runat="server" TargetControlID="PnlContent" ExpandControlID="PnlTitle" 
            CollapseControlID="PnlTitle" TextLabelID="Label1" 
            CollapsedText="Show Details (...)" ExpandedText="Hide Details (...)" 
            ImageControlID="Image1" ExpandedImage="images/collapse_blue.jpg" 
            CollapsedImage="images/expand_blue.jpg"
            Collapsed="True" SuppressPostBack="true">
        </cc1:CollapsiblePanelExtender>

css

.collapsePanel {
      width: 200px;
      height:0px;
      background-color:white;
      font-family: Georgia, "Times New Roman", Times, serif;
	  font-size: 13px;
	  color: #666666;
      position:relative;
}
 
.collapsePanelHeader
{
	width: 200px;
	height: 20px;
	background-color: #0066CC;
	font-weight: bold;
	float: none;
	padding: 5px;
	cursor: pointer;
	vertical-align: middle;
	font-family: Georgia, "Times New Roman", Times, serif;
	font-size: 13px;
	color: #666666;
	position:relative;
}

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