document.getElementById("letters").onkeyup = function() {
	updateCities();
};
function updateCities() {
	if (document.getElementById("letters").value != "" && entered_text != document.getElementById("letters").value) {
		request.abort();
		request.open("POST", url + "?action=...&letters=" + document.getElementById("letters").value + "&rand=" + Math.random(), true);
		request.onreadystatechange = behaviorCities;
		request.send(null);
	} else if (document.getElementById("letters").value == "") {
		request.abort();
		entered_text = "";
		document.getElementById("city").options.length =  0 ;
	}
}
function behaviorCities() {
	if (request.readyState ==  4 ) {
		document.getElementById("city").options.length =  0 ;
		var cities = request.responseXML.getElementsByTagName("c");
		for (var i =  0 ; i < cities.length; i++) {
			if (cities[i].attributes[ 0 ].value == "#city")
				document.getElementById("city").options[i] = new Option(cities[i].attributes[ 1 ].value, cities[i].attributes[ 0 ].value, true, true);
			else document.getElementById("city").options[i] = new Option(cities[i].attributes[ 1 ].value, cities[i].attributes[ 0 ].value);
		}
	}
}