急用.net如何实现点击小图看大图，因为现在点击进去后的图片特别小，不管我在后台上传多大的图片，它都显示那么小

急用.net如何实现点击小图看大图？www.gzcall.com这个是我的网站，我想点击首页的热卖产品下面的图片时能看到大图，因为现在点击进去后的图片特别小，不管我在后台上传多大的图片，它都显示那么小；这个是首页的热卖产品下面的图片的代码<asp:DataList Width="546" runat="server" RepeatColumns="4" ID="dlstGiftCert">
                                <ItemStyle Width="25%" HorizontalAlign="center" />
                                <ItemTemplate>
                                    <table width="80%" cellpadding="0" cellspacing="0" border="0">
                                        <tr>
                                            <td style="height: 83px; border: 1px dotted #dddddd; padding: 1px">
                                                <%# Utility.MakeImage("giftcert_" + Eval("Id"), (byte[])Eval("Picture"), "giftcertshow.aspx?Id=" + Eval("Id"), 100, 100) %>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td style="height: 24px">
                                                <b>
                                                    <%# Utility.WriteHyperLink(Eval("Name"), Eval("Id"), "giftcertshow.aspx?Id={0}", 6, null) %>
                                                </b>
                                            </td>
                                        </tr>
                                        <tr>
                                            <td style="height: 24px">
                                                <b><font color="#f36600">所需积分：<%# Eval("Score") %></font></b></td>
                                        </tr>
                                    </table>
                                </ItemTemplate>
                            </asp:DataList>
点击进去后的图片的代码是：
  <asp:Literal ID="ltiPic" runat="server"></asp:Literal>
求各位高手详细指点下，因为我是新手，谢谢、、、

补充：.NET技术 ,  ASP.NET