Ok allora ho creato un nuovo sito web ajax.
Mi ha creato lui il web config

E ho messo questo codice:
codice:
<form id="form1" runat="server">
        <asp:ScriptManager ID="ScriptManager1" runat="server" />
        <asp:Timer ID="Timer1" runat="server" Interval="3000">
        </asp:Timer>
        <div>
        <asp:updatepanel ID="Updatepanel1" runat="server" >
            <ContentTemplate>
                
                <asp:Image ID="BannerImage" runat="server" ImageUrl="banner/banner_1.gif" />
            </ContentTemplate>
            <Triggers>
                <asp:AsyncPostBackTrigger ControlID="Timer1"/>
            </Triggers>
        </asp:updatepanel>
        </div>
</form>

codice:
Partial Class _Default
    Inherits System.Web.UI.Page

    Protected Sub Timer1_Tick(ByVal sender As Object, ByVal e As EventArgs)
        Dim n As Integer = New Random().Next(1, 9)
        BannerImage.ImageUrl = "banners/Banner_" + n.ToString + ".gif"
    End Sub
End Class
Uso VS 2005 Net 2.0