What's the best practice for using AJAX Flicker?

Your TargetPanel is here
<asp:Panel ID="panelPost" runat="server" CssClass="cpBody">
<div>
//Ur collapsible Content
</div>
</asp:Panel>
And now we are preventing the flickering by the CSS style and the style is as follows.
.cpBody
{
height:0px;
overflow: hidden;
}