var t_scroll;

function moveDown(){
  try{
    var o_top = parseInt(o_scroll.style.top);
    if ((o_top + o_scroll.offsetHeight) > o_cont.offsetHeight) {
      var n_top = o_top - n_speed;
      if ((n_top + o_scroll.offsetHeight) <= o_cont.offsetHeight) { 
        n_top = o_cont.offsetHeight - o_scroll.offsetHeight ;
        o_scDown.style.visibility = 'hidden';
      }
      if (n_top < 0) {
        o_scUp.style.visibility = 'visible';
      }
      o_scroll.style.top = n_top + 'px';
      
      t_scroll = setTimeout('moveDown()', f_delay * 1000);
    }
    return true;
  } catch(e) {}
}

function moveUp(){
  try{
    var o_top = parseInt(o_scroll.style.top);    
    if (o_top < 0) {
      var n_top = o_top + n_speed;
      if (n_top >= 0) {
        n_top = 0;
        o_scUp.style.visibility = 'hidden';
      }
      if ((n_top + o_scroll.offsetHeight) > o_cont.offsetHeight) {
        o_scDown.style.visibility = 'visible';
      }
      o_scroll.style.top = n_top + 'px';
      
      t_scroll = setTimeout('moveUp()', f_delay * 1000);
    }
    return true;
  } catch(e) {}
}

function stopMove() {
  clearTimeout(t_scroll);
}