function disp(id_obj)
{
var dsp =document.getElementById(id_obj).style;
var himg =document.getElementById('himg'+id_obj);
dsp.display = (dsp.display != 'block' ? 'block' : 'none');
if (himg!=null){
himg.src = (himg.src.indexOf('gr_pl') != -1 ? himg.src.replace('gr_pl','gr_mn') : himg.src.replace('gr_mn','gr_pl'));
}
}