Changing a control attribute at runtime.

Hi Guys,
I'm basically trying to get a div containing a loading gif to show on my page at runtime. I call it from a button click event as well as in the code flow. It was working before I used the AJAX Update Panels. I've since taken them out as they were causing issues with RegisterClientScriptBlock. By the way, does commenting out the AJAX Markup like this...
<%-- <asp:UpdatePanel ID="up_search" runat="server"> <ContentTemplate>--%>
...remove them from influence? My div markup looks like this..<div id="loading" style="visibility: hidden;" runat="server"> <img id="loading_gif" alt="Loading...& ...