function muestraVentana(pagina,fs,an,al)
{
	var ancho=(an?an:450);
	var alto=(al?al:550);

	window.open(pagina,"mellow_popup_"+Math.round(Math.random()*50000),"toolbar=no, location=no, directories=no, status=no, menubar=no, scrollbars=yes, resizable=yes, width="+(fs?screen.availWidth:ancho)+", height="+(fs?screen.availHeight:alto)+", left="+(fs?"0":(screen.availWidth-ancho)/2)+", top="+(fs?"0":((screen.availHeight-alto)/2)-25));
}