Remove button box

I'm writing an application in C and I've a GtkLinkButton that contains a GtkStockItem. How can I remove the button box that appears when mouse pointer is on and when I click it?

EDIT

Thanks very much, but it doesn't work. This is the output:

"Gtk-WARNING **: filed to set text from markup due to error parsing markup: Unknow tag 'a' on line 1 char 38

GLib-GObject-WARNING **: gsignal.c:2267: sigal activate-link' is invalid for istance0x8081860'

Gtk-WARNING **: filed to set text from markup due to error parsing markup: Unknow tag 'a开发者_开发知识库' on line 1 char 38"

I study GTK libraries since few time, but I think that you can't use all html tags that you want in gtk_label_set_markup() function (tag 'a' is one). I understand that you can only use Pango text markup language (http://library.gnome.org/devel/pango/stable/PangoMarkupFormat.html), so you can't use tag 'a' or not directly.

gtk_button_set_relief(GTK_BUTTON(link_button), GTK_RELIEF_NONE);

Addenum:

Yes, you are right! There is no way to let a GtkButton behaves in that way (and to my eyes, GTK_RELIEF_HALF and GTK_RELIEF_NORMAL looks the same).

You could use a GtkLabel instead. In C, that would be something like:

label = gtk_label_new(NULL);
gtk_label_set_markup(GTK_LABEL(label), "<a href='http://www.gtk.org'>GTK+ home</a>");

Example:

I really hate to do your homeworks... Anyway I'm feeling great, so here it is a fully working example:

/*
gcc `pkg-config --cflags gtk+-2.0` link.c \
    -o link `pkg-config --libs gtk+-2.0`
*/
#include <gtk/gtk.h>

static gboolean
my_dialog(GtkWindow *top_level)
{
    GtkWidget *dialog = gtk_message_dialog_new(top_level,
                                               GTK_DIALOG_MODAL,
                                               GTK_MESSAGE_INFO,
                                               GTK_BUTTONS_CLOSE,
                                               "This is a test message");

    gtk_dialog_run(GTK_DIALOG(dialog));
    gtk_widget_destroy(dialog);

    return TRUE;
}

int
main(int argc, char *argv[])
{
    GtkWidget *window, *label;

    gtk_init(&argc, &argv);

    window = gtk_window_new(GTK_WINDOW_TOPLEVEL);

    label = gtk_label_new(NULL);
    gtk_label_set_markup(GTK_LABEL(label),
                         "<a href='http://www.gtk.org'>GTK+ web site</a>");
    g_signal_connect_swapped(label, "activate-link",
                             G_CALLBACK(my_dialog), window);
    gtk_container_add(GTK_CONTAINER(window), label);

    gtk_widget_show_all(window);
    gtk_main();

    return 0;
}