function AbrirVentana(url,ancho,alto)
{		
	var ventana;
	var winl;
	var wint;
	var h;
	var w;

	h=alto;
	w=ancho;
	winl = (screen.width - w) / 2;
	wint = (screen.height - h) / 2;

    var myrandom=Math.round(Math.random()*2)
	ventana = open(url ,'v'+myrandom,'toolbar=0,location=0,directories=0,status=0,menubar=0,scrollbars=1,resizable=yes,width=' + w + ',height=' + h + ',left=' + winl +',top=' + wint);
	ventana.focus;
}