Hi,
You could use System.Threading to do it.
Its very simple and its very sweet too ;-)
Add namespace to your project like
using System.Threading;
If you want to clear it in Button Click event then use the below code
protected void Button1_Click(object sender, EventArgs e)
{
Thread.Sleep(1200);
Label1.Text = "";
}
Hope this helps you a bit.
Regards,
RK