<asp:gridview id="GridView3" runat="server" horizontalalign="Center" autogeneratecolumns="False" style="border-color: #808000; top: 450px; left: 515px; position: absolute; height: 84px; width: 384px" pagesize="3" allowpaging="true" onpageindexchanging="GridView3_PageIndexChanging" onselectedindexchanged="GridView3_SelectedIndexChanged" xmlns:asp="#unknown">
</asp:gridview>
Implement pageindex changing as below
protected void GridView3_PageIndexChanging(object sender, GridViewPageEventArgs e)
{
GridView3.PageIndex = e.NewPageIndex;
GridView3.DataBind();
}