Add/Bind event handlers explicitly as in following script.
eg. OnRowEditing="GridView1_RowEditing"
<asp:gridview id="GridView1" runat="server" backcolor="#CCCCCC" bordercolor="#999999" borderstyle="Solid" borderwidth="3px" cellpadding="4" cellspacing="2" forecolor="Black" autogeneratecolumns="False" allowpaging="True" pagesize="25" onrowediting="GridView1_RowEditing"> </asp:gridview>