Disable Label after some amount of time

Achieve the same using AJAX AnimationExtender control.

Use the below code:

<asp:updatepanel id="upnl" runat="server" xmlns:asp="#unknown">
    <contenttemplate>
         <asp:label id="lbl" runat="server" cssclass="fadeLabel"></asp:label>
    </contenttemplate>
</asp:updatepanel>

<asp:updatepanelanimationextender id="upax" runat="server" behaviorid="animation" targetcontrolid="upnl" xmlns:asp="#unknown">
    <animations>
        <onupdated>  
            <sequence>  
                <ScriptAction Script="fadeOut()" />
            </sequence>  
        </onupdated>   
    </animations>  
</asp:updatepanelanimationextender>

in your code behind.

lbl.Text = "Assign Text";
upnl.Update();

Fadeout method:

function BannerOut() {
    $(".fadeLabel").fadeOut(1000);
}

Thanks
--RA