var addEvent = function(evt, handler) {
	if (window.addEventListener) {
		document.addEventListener(evt, handler, false);
	} else if (window.attachEvent) {
		document.attachEvent('on' + evt, handler);
	}
};
var removeEvent = function(evt, handler) {
	if (window.removeEventListener) {
		document.removeEventListener(evt, handler, false);
	} else if (window.detachEvent) {
		document.detachEvent('on' + evt, handler);
	}
};