CSS messing up in updatepanel

Question

So I have an update panel.

The css for it is as follows

#<%=mypanel.ClientID%> 
{
    border-style:inset;
    border-color: #724229;
    background-color: #AD816B;
    position: absolute;
}

So this works. Inside of the update panel I also have a scrollbar. It works fine when I load the page but for some reason when something updates inside the panel the css on the scrollbar messes up.

(Normal bar)

(after update)

I can't figure out why it is doing this. Looked up why it would be doing this but haven't found anything, only on Jquery but it is not using jquery it's all css.

update panel html

  <asp:UpdatePanel ID="UpdatePanel1" runat="server" class="notifications" UpdateMode="Conditional"
            ChildrenAsTriggers="true">
            <ContentTemplate>
                <div class="mCustomScrollbar content3 fluid light">
                    <table>
                        <tr>
                            <td style="width: 15%">
                                Action
                            </td>
                            <td style="width: 55%">
                                Description
                            </td>
                            <td style="width: 30%">
                                Date Added
                            </td>
                        </tr>
                        <tr>
                            <td>
                            </td>
                            <td>
                            </td>
                            <td>
                            </td>
                            <td>
                            </td>
                        </tr>
                    </table>
                </div>
            </ContentTemplate>
        </asp:UpdatePanel>

Answer 1

Wrap the update panel with an asp Panel control as in code below and add CSS styling to asp Panel control and not to UpdatePanel.

You should not apply CSS to update panel. For this reason, it does not have a property of CssClass unlike other web controls.

<asp:Panel id="panel1" runat="server" 
          CssClass ="notifications mCustomScrollbar content3 fluid light">
  <asp:UpdatePanel ID="UpdatePanel1" runat="server"  UpdateMode="Conditional"
        ChildrenAsTriggers="true">
        <ContentTemplate>
            <div>
                <table>
                    <tr>
                        <td style="width: 15%">
                            Action
                        </td>
                        <td style="width: 55%">
                            Description
                        </td>
                        <td style="width: 30%">
                            Date Added
                        </td>
                    </tr>
                    <tr>
                        <td>
                        </td>
                        <td>
                        </td>
                        <td>
                        </td>
                        <td>
                        </td>
                    </tr>
                </table>
            </div>
        </ContentTemplate>
    </asp:UpdatePanel>
</asp:Panel>