asp.net在后台指定事件,在FF下不兼容的问题

<asp:GridView ID="gvCart" runat="server" DataKeyNames="spGoodId" AutoGenerateColumns="False"
            Width="866px" OnRowDataBound="gvCart_RowDataBound"
            OnRowDeleting="gvCart_RowDeleting" 
            onpageindexchanging="gvCart_PageIndexChanging"  
            ShowFooter="true">
    <Columns>
......
<asp:TemplateField HeaderText="数量"  HeaderStyle-BackColor="#FF870F" HeaderStyle-ForeColor="#ffffff">
  <ItemTemplate>
    <img class="img1" src="../../images/bo.gif" id="imgReduce" runat="server" alt="" />
      <asp:TextBox ID="txtAmount" Width="20px" Height="16px" runat="server" Text='<%# Eval("Amount") %>'
             MaxLength="2" autocomplete="off"></asp:TextBox>
      <img class="img1" src="../../images/bc.gif" id="imgPlus" runat="server" alt=""/>
   </ItemTemplate>
</asp:TemplateField>
......
   </Columns>          
</asp:GridView>        //点+，数量+1
        function Plus(obj) {
            var oj1=obj.value.replace(/[^\d]/g, '');
            if(oj1==''||oj1=='NaN'){
              obj.value=1;
            }else{
              obj.value = parseInt(obj.value) + 1;
            }
        }
        //数量-1
        function Reduce(obj) {
          var oj2=obj.value.replace(/[^\d]/g, '');
          if(oj2==''||oj2=='NaN'){
          }else{
            if (obj.value > 1) {
                obj.value = obj.value - 1;
            }
          }
        }protected void gvCart_RowDataBound(object sender, GridViewRowEventArgs e){
......
TextBox tb = (TextBox)e.Row.FindControl("txtAmount");
((HtmlImage)e.Row.FindControl("imgReduce")).Attributes.Add("onclick", "Reduce(" + tb.ClientID + ")");
((HtmlImage)e.Row.FindControl("imgPlus")).Attributes.Add("onclick", "Plus(" + tb.ClientID + ")");
......
}在FF下 这2个click事件  怎么触发不了,点击imgReduce和imgPlus  这2个图片按钮  没效果！
大家帮帮忙！！！