function toggleElementVis(a_id){
	var id = a_id;
	var current;
	if (document.getElementById){ // vista?
		current = (document.getElementById(id).style.visibility == 'visible') ? 'hidden' : 'visible';
		document.getElementById(id).style.visibility = current;
	}else if (document.all){
		current = (document.all[id].style.visibility == 'visible') ? 'hidden' : 'visible';
		document.all[id].style.visibility = current;
	}else if (document.layers){
		current = (document.layers[id].visibility == 'visible') ? 'hidden' : 'visible';
		document.layers[id].visibility = current;
	}
}