Google Map ~ on map moved event

this is an example, when move map alert map's latitude, longitude

GEvent.addListener(map, "moveend", function() {
var lat = map.getCenter().lat();
var lng = map.getCenter().lng();

alert(lat);
alert(lng);
});

reference
http://code.google.com/intl/zh-TW/apis/maps/documentation/javascript/v2/events.html