HTML Editor inside Ajax Collapsible Panel Extender not being displayed in IE 6 for asp.net web page

I have a Ajax HTMLEditor in my web page inside a panel which is targeted by the collapsible panel extender.

When the panel is expanded, there is a big empty space without any of the controls inside the panel being displayed.

The issue here is the panel is expanded but there is nothing visible inside it including any buttons and the Html editor. When i scroll up and down though the controls sometimes become visible.

<cc1:CollapsiblePanelExtender ID="ColPnlExtEvents" runat="server" TargetControlID="pnlAddContentEvents"
                BehaviorID="ColPnlExtEventsBehavior" TextLabelID="lblShowEvents" SuppressPostBack="true"
                CollapsedImage="~/images/expand.jpg" ExpandedImage="~/images/collapse.jpg" CollapsedText="(Show Details...)"
                ExpandedText="(Hide Details...)" ImageControlID="ImgBtnEvents" Collapsed="True" CollapsedSize="1"
        开发者_StackOverflow社区        CollapseControlID="pnlEvents" ExpandControlID="pnlEvents">
            </cc1:CollapsiblePanelExtender>
            <asp:Panel Style="cursor: pointer" ID="pnlEvents" runat="server" CssClass="collHeader">
                <div style="padding: 2px; cursor: pointer; vertical-align: middle;">
                    <div style="float: left;">
                        <asp:Label ID="abnormalEventsLabel" runat="server">Add Abnormal Events</asp:Label></div>
                    <div style="float: left; margin-left: 20px;">
                        <asp:Label ID="lblShowEvents" runat="server">(Show Details...)</asp:Label>
                    </div>
                    <div style="float: right; vertical-align: middle;">
                        <asp:ImageButton ID="ImgBtnEvents" runat="server" ImageUrl="~/images/expand.jpg"
                            AlternateText="(Show Details...)" />
                    </div>
                </div>
            </asp:Panel>
            <asp:Panel Style="overflow: hidden" ID="pnlAddContentEvents" runat="server" CssClass="collPanel"
                Height="0px">
                <table id="tblEventsDetails" width="100%" runat="server">
                    <tr>
                        <td align="left">
                            <a class="labelText">Description</a>
                        </td>
                        <td style="width: 75%">
                            <uc:RichTextBox ID="abnormalEventsDescriptionRichTextBox" runat="server" />
                        </td>
                    </tr>
                    <tr>
                        <td class="blankRow">
                        </td>
                    </tr>
                    <tr>
                        <td colspan="2" align="right">
                            <asp:LinkButton CssClass="btnSimpleSave" ID="abnormalEventSaveLinkButton" runat="server"
                                OnClick="abnormalEventSaveLinkButton_Click" OnClientClick="javascript:return ParticularClosureRichTextBoxValidation('ctl00_cphMain_abnormalEventsDescriptionRichTextBox_HTMLText','Abnormal Events');">Save</asp:LinkButton>
                            <asp:LinkButton CssClass="btnSimpleCancelForSubSections" ID="abnormalEventCancelLinkButton"
                                runat="server" CausesValidation="false" OnClick="abnormalEventCancelLinkButton_Click">Cancel</asp:LinkButton>
                        </td>
                    </tr>
                </table>
            </asp:Panel>

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Many times, different JS libraries does not mix well today - you might have encountered the same.

Personally, I prefer pure js based approaches (such as jquery or jquery plugin) over control based approaches (as done in Ajax Control Toolkit). For collapsible panel, you can use jquery sliding functions. For example, see this fiddle that I had put up for another SO question to illustrate multiple collapsible panels