function popup(url, nombre, ancho, alto) {
   var izq = (screen.width - ancho) / 2;
   var arr = (screen.height - alto) / 2;
   window.open(url, nombre, 'width=' + ancho + ',height=' + alto + ',left=' + izq + ',top=' + arr + ',' + 'scrollbars=1,toolbar=0,menubar=0,statusbar=0,location=0');
 }
 

var StayAlive = 5; // Number of seconds to keep window open
function KillMe(){
setTimeout("self.close()",StayAlive * 1000);
}