function display_menu(obj, first, last){
	var el = document.getElementById("fils"+obj);
	if(el.style.display != "block"){
		el.style.display = "block";	
		document.getElementById("menu"+obj).className='lien_menu_principal'+((first===true)?'_first':((last===true)?'_last':''))+'_actif';
	}else{
		el.style.display = "none";		
		document.getElementById("menu"+obj).className='lien_menu_principal'+((first===true)?'_first':((last===true)?'_last':''));
		
	}
}