var current = 0;

Effect.DefaultOptions = {
  transition: Effect.Transitions.sinoidal,
  duration:   0.3,   // seconds
  fps:        25,   // 100= assume 66fps max.
  sync:       false, // true for combining
  from:       0.0,
  to:         1.0,
  delay:      0.0,
  queue:      'parallel'
}

$('tabs').firstDescendant().className += ' active-tab';
var active_tab = $('tabs').firstDescendant().firstDescendant().firstDescendant();
var motion = false;
function move_to(to, el){    
  if (!motion) {if (active_tab != el) {
el.parentNode.parentNode.className += ' active-tab';
   
active_tab.parentNode.parentNode.className = 'corner-left-top';
   }
   active_tab = el;    
move = (current - to)*701;
new Effect.Move($('tabber'), { x: move, beforeStart:function(){ motion = true;},afterFinish:function(){motion = false;}});
current = to;
  }
}