var popWnd; //Objeto ventana de popup

  function abrir(htmlfile, wndWidth, wndHeight) {
    var maxWidth = screen.width-10;
    var maxHeight = screen.height-56;

    //Preprocesado de parámetros
    if (wndHeight==0) wndHeight = maxHeight;
    if (wndWidth==0) wndWidth = maxWidth;

    //Calculo de la posición para centrar la ventana
    var posX = maxWidth/2 - wndWidth/2;
    var posY = maxHeight/2 - wndHeight/2;

    if (popWnd) popWnd.close();
    popWnd = open(htmlfile, 'popup', 'resizable=0,toolbar=0,scrollbars=1,location=0,directories=0,status=0,menubar=0,width='+wndWidth+',height='+wndHeight+',screenX=0,screenY=0,left='+posX+',top='+posY);

    //this.blur();
    popWnd.focus();
  }