Page is refreshing inside update panel

Hi

I have added update panel and gridview in my page. When I click on any Image Button which is in Gridview, the page refreshes at that time. I don't want my page to refresh. Please see my code and tell me where it is going wrong.

Code:

             <div class="Support"> <h1><asp:Label ID="lblTransactionStatus" runat="server" ></asp:Label></h1> <br /> <table width="100%"> <tr id="Success" runat="server" visible="false"> <td colspan="2"> <asp:Label ID="lblTransactionMessage" runat="server" ></asp:Label> </td> </tr> <tr > <td style="width:30%" > Your Order Number : </td> <td > <asp:Label ID="lblOrderID" runat="server" ></asp:Label> </td> </tr> <tr > <td style="width:30%"> Your Email : </td> <td > <asp:Label ID="lblUserEmail" runat="server" ></asp:Label> </td> </tr> <tr > <td valign="top" style="width:30%"> Your Order Products : </td> <td valign="top" > <asp:UpdatePanel ID="ProductPanel" runat="server" ChildrenAsTriggers="true"> <ContentTemplate> <asp:GridView ID="gvProducts" ShowHeader="false" runat="server" BorderStyle="None" BorderWidth="0px" AutoGenerateColumns="false" DataKeyNames="Product_Name,ProductID,Product_Image" Width="100%" onrowcommand="gvProducts_RowCommand"> <Columns> <asp:TemplateField> <ItemTemplate> <asp:Label ID="lblProduct" runat="server" Text='<%# DataBinder.Eval(Container.DataItem,"Product_Name") %>'></asp:Label> </ItemTemplate> </asp:TemplateField> <asp:TemplateField> <ItemTemplate> <asp:ImageButton ID="imgFB" runat="server" CommandName="FB" CommandArgument='<%# Eval("ProductID")+ "|" + Eval("Product_Name")+ "|" + Eval("Product_Image")%>' ImageUrl=facebook_ico-1.gif" /> &nbsp;<asp:ImageButton ID="imgTwitter" CommandName="twit" runat="server" CommandArgument='<%# Eval("ProductID")+ "|" + Eval("Product_Name")+ "|" + Eval("Product_Image")%>' ImageUrl=twitter_ico.gif" /> &nbsp;<asp:ImageButton ID="imgGoogle" CommandName="Google" runat="server" CommandArgument='<%# Eval("ProductID")+ "|" + Eval("Product_Name")+ "|" + Eval("Product_Image")%>' ImageUrl="ico-google-plus.png" /> &nbsp;<asp:ImageButton ID="imgPint" CommandArgument='<%# Eval("ProductID")+ "|" + Eval("Product_Name")+ "|" + Eval("Product_Image")%>' CommandName="PINIT" runat="server" ImageUrl="icon-pinterest.png" /> </ItemTemplate> </asp:TemplateField> </Columns> </asp:GridView> </ContentTemplate> <Triggers> <asp:PostBackTrigger ControlID="gvOrders" /> </Triggers> </asp:UpdatePanel> </td> </tr> <tr > <td style="width:30%"> Amount : </td> <td > <asp:Label ID="lblAmount" runat="server" ></asp:Label> </td> </tr> <tr > <td style="width:30%"> Your Transaction Response Message : </td> <td > <asp:Label ID="lblTransactionRespMsg" runat="server" ></asp:Label> </td> </tr> </table> <br /> <br /> </div>