var top2 = 0;
  var counter = 0;
  var rollHeight = 100;
  var actualLimit = 0; 
  var time = 5; 
  var t;
  var cos;
  
  
  function stopCount()
  {
    clearTimeout(t);
  }

  function moveDown(){
    var x = $('ps_projects').getStyle('height');
    var len = x.length;
    x= x.slice(0, len-2);
    x=Number(x);

    if(((-actualLimit)+rollHeight) < x){
     actualLimit -= rollHeight;
     down();
    } 
    
  }
  
  function moveUp(){
    if(actualLimit < 0)
    {
     actualLimit += rollHeight;
     up();
    }
  }
    
  function down(){
    
    var main = $('main_menu_under').getStyle('height');
    var len = main.length;
    main= main.slice(0, len-2);
    main=Number(main);

    var proj = $('ps_projects').getStyle('height');
    var len = proj.length;
    proj= proj.slice(0, len-2);
    proj=Number(proj);

    if((top2+ proj) > main){
      top2 -=1;
      $('ps_projects').setStyle({ top:  top2+'px' });
      t=setTimeout("down()",time);
    }
    else
    {
      stopCount();
    }
    if(top2<=actualLimit){
      stopCount();
    }
  }
  
  function up(){
    top2 +=1;
   $('ps_projects').setStyle({ top:  top2+'px' });
    t=setTimeout("up()",time);
    if(top2 >= actualLimit){
      stopCount();
    }
  }