function hideshow(num) {
	if (document.getElementById('tree_'+num).style.display=='none') {
		document.getElementById('tree_'+num).style.display = 'block';
		document.getElementById('par_'+num).style.backgroundImage = 'url("/_img/-.jpg")';
	} else {
		document.getElementById('tree_'+num).style.display = 'none';
		document.getElementById('par_'+num).style.backgroundImage = 'url("/_img/+.jpg")';
	}
	return false;
}