How to fire Link Button in Firefox

function fnEnterkey(e) {

                if (e.keyCode == "13") {

                    var button = document.getElementById("<%=lnkButton.ClientID%>");

                    if (button.dispatchEvent) {

                        var e = document.createEvent("MouseEvents");

                        e.initEvent("click", true, true);

                        if (button.dispatchEvent(e))

                        { __doPostBack("<%=lnkButton.UniqueID %>"); }

                         return false;

                    }

                    else {

                        button.click();

                        return false;

                    }

                }

            }

........

    <asp:Panel ID="pnlButton" runat="server" DefaultButton="lnkButton" onkeypress="return fnEnterkey(event);">

                     

                      <asp:LinkButton ID="lnkButton" Text="Search" runat="server" CausesValidation="false"

                                       OnClientClick="return CheckEmptyQuery();"  OnClick="lnkButton_Click" CssClass="LButton"></asp:LinkButton>

                                    …..

</asp:Panel>

........