var sessionHolderImage = new Image(110,20);
  var t = 1 * 60 * 1000;
  function holdSession()
  {
    //clearTimeout(t);
    sessionHolderImage.src = "http://www.povleceni-luzkoviny.cz/sessionHolder.php?image=true&changer="+(Math.random()*100);
    //alert(sessionHolderImage.src);
    setTimeout(holdSession, t);
  }
  setTimeout(holdSession, t);