function popUp(sitio, ancho, alto){
	ancho = ancho < 10 ? 400 : ancho;
	alto = alto < 10 ? 300 : alto;
	x = 100;
	y = 100;
	if (parseInt(navigator.appVersion) > 3) {
		x = (screen.width - ancho) / 2 + (ancho/2);
		y = ((screen.height - alto) / 2) - 100;
		if(x + ancho > screen.width){
			x = screen.width - ancho - 200;
		}
	}
	newWin = window.open(sitio, "media", "toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=0,hscrollbar=0,,copyhistory=1,width=" + ancho + ",height=" + alto + ",top=" + y + ",left=" + x);
	newWin.focus();
}