var popup_url = "popup_tarjetas.htm"
	var derecha=(screen.width)/2; 
	var arriba=(screen.height)/2; 
	var atributos ="toolbar=0,scrollbars=1,location=0,statusbar=0,menubar=0,resizable=0,width=650,height=600,left=20 ,top=20"; 
	var pop_under = 0 //1-sera un "pop under", es decir, no se muestra como ventana activa

	function popup(){
		 popup_vfmail = window.open( popup_url, "popup_tarjetas.htm", atributos)
		return;
	}