<asp:GridView ID="grdweekly" runat="server"  CssClass="GridReport" OnRowDataBound="grdweekly_RowDataBound"> 
                                    <asp:Image ID="Image1" runat="server" ImageUrl="Images/Elephant.png" />
                                    <asp:Label ID="Label2" runat="server" Text='<%#Eval("WeekNo") %>'></asp:Label>
protected void btnwexport_Click(object sender, EventArgs e)
    {
        Response.Clear();
        Response.Buffer = true;
        Response.AddHeader("content-disposition", "attachment;filename=WeeklyECGReport.xls");
        Response.Charset = "";
        Response.ContentType = "application/vnd.ms-excel";
        using (StringWriter sw = new StringWriter())
        {
            HtmlTextWriter hw = new HtmlTextWriter(sw);
            //To Export all pages
            //grddaily.AllowPaging = false;
            this.fillgrid();
            grdweekly.HeaderRow.BackColor = Color.White;
            foreach (TableCell cell in grdweekly.HeaderRow.Cells)
            {
                cell.Width = 140;
                cell.Height = 190;
                break;
            }
            grdweekly.RenderControl(hw);
            //style to format numbers to string
            string style = @"<style> .textmode { } </style>";
            Response.Write(style);
            Response.Output.Write(sw.ToString());
            Response.Flush();
            Response.End();
        }
    }
 
Pls Help me.. Its very urgent.