function parseQueryString (str) {
	str = str ? str : location.search;
	var query = str.charAt(0) == '?' ? str.substring(1) : str;
	var args = new Object();
	if (query) {
		var fields = query.split('&');
		for (var f = 0; f < fields.length; f++) {
			var field = fields[f].split('=');
			args[unescape(field[0].replace(/\+/g, ' '))] = 
			unescape(field[1].replace(/\+/g, ' '));
		}
	}
	return args;
}

function menu_referer_selector() {
	if(document.referrer) {
		var f=document.referrer;
	} else {
		var f=top.document.referrer;
	}
	if (f) {
		var args = parseQueryString (f);
		for (var arg in args) {
			if ( arg == 'tree_id' ) {
				var id = 't' + args[arg];
				e = document.getElementById(id);
				if (e) {
					e.className = 'attiva';
				}
			}
		}
	}
}