You can use Ajax, it is very easy
<asp:updatepanel id="updateconfiguration" runat="server" xmlns:asp="#unknown">
Some Stuff
<asp:UpdateProgress ID="UpdateProgress1" runat="server" AssociatedUpdatePanelID="updateconfiguration">
<ProgressTemplate>
<img src="../Images/loadGreen.gif" />
</ProgressTemplate>
</asp:UpdateProgress>