Keep panel visible and open if clicked Ajax Drop Down Extender

Hello,

Trying to "drop" dropdownextendered panel if any where clicked on Panel.

Items populating programatically.

When setting first item (LinkButton) OnClientClick="HidePanels()" and (DropDownExtende) OnClientPopup="HidePanels()" disappearing theme, working in Chrome but doesnt work in IE "0x800a139e - JavaScript runtime error: Sys.InvalidOperationException: Handler must be a function." with this message.

Found a solution that removing brackets but after removing doesnt fire event both of browsers. 

I need to achieve that panel always visible and dropped if user clicked anywhere of panel.

<script type="text/javascript">
         function HidePanels() {
             var panel = document.getElementById("Panel");
                if (panel.style.visibility == 'hidden') {
                    panel.style.visibility = 'visible';
                }
                else {
                    panel.style.visibility = 'hidden';
                }
            }</script>   <script language="javascript" type="text/javascript">
            function DropDownExtender1_pageLoad() { $find('DDE').unhover = doNothing; $find('DDE')._dropWrapperHoverBehavior_onhover(); 
            } 
            function doNothing() {}

Sys.Application.add_load(DropDownExtender1_pageLoad);

        </script><ContentTemplate>                          <div id="divdisplayadresses">                               <div id="divdisplaydelivery" style="float: left; width: 250px;"><asp:LinkButton runat="server" ID="LinkButtonPanelDeliveryAdress" OnClientClick="HidePanels()"
                                   Style="display: block; width: 250px; height:150px; padding: 2px; padding-right: 50px; font-family: Tahoma; font-size: 11px;" /><asp:Panel runat="server" ID="Panel" ><ajaxToolkit:DropDownExtender runat="server" ID="DDE" 
                                    TargetControlID="LinkButtonPanelDeliveryAdress" DropDownControlID="Panel" OnClientPopup="HidePanels()"  Enabled="true"/></asp:Panel>                                                          </div></ContentTemplate>