radiobutton not working inside update panel?

Hi

why is this noty working

I have the below code when I click yes/no radiobutton nothing happens,why?

<tr><td><asp:ScriptManager runat="server"></asp:ScriptManager> <asp:UpdatePanel runat="server"><ContentTemplate>  on Site :  <asp:Radiobutton runat="server" ID="Radiobutton1" Text="Yes" AutoPostBack="true" GroupName="e1" OnCheckedChanged="Radiobutton1_CheckedChanged" /><asp:Radiobutton runat="server" Groupname="e1" autopostback="true" ID="Radiobutton2" Text="No" OnCheckedChanged="Radiobutton2_CheckedChanged"/></ContentTemplate></asp:UpdatePanel>

 Protected Sub Radiobutton1_CheckedChanged(sender As Object, e As EventArgs)
        GridView1.Visible = True
    End Sub
    Protected Sub Radiobutton2_CheckedChanged(sender As Object, e As EventArgs)
        GridView1.Visible = False
    End Sub