<asp:Button ID="ibtn" runat="server" Text="wait" UseSubmitBehavior="false" OnClientClick="document.getElementById('ibtn').disabled=true" OnClick="ibtn_Click" />
<asp:Button ID="ibtn" runat="server" Text="wait" UseSubmitBehavior="false" OnClientClick="document.getElementById('ibtn').disabled=true" OnClick="ibtn_Click" />