function windowOpen(_url, _target, _width, _height) {
	var _left = Math.round((window.screen.availWidth - _width) / 2);
	var _top = Math.round((window.screen.availHeight - _height) / 2);
	window.open(_url, _target, "scrollbars=yes, resizable=yes, width=" + _width + ", height=" + _height + ", left=" + _left + ", top=" + _top);
	return false;
}