function popup(url, width, height) {
	var left = screen.width / 2 - width / 2;
	var top  = screen.height / 2 - height / 2;
	
	newwindow = window.open(url, 'popup', 'width=' + width + ',height=' + height + ',left=' + left + ',top=' + top);
	
	if (window.focus) {
		newwindow.focus()
	}
	
	return false;
}