$(function() {
    var step = 1; 
    var current = 0; 
    var maximum = $('#my_carousel ul li').size(); 
    var visible = 1; 
    var speed = 300; 
    var liSize = 900;
    var carousel_height = 435;
 
 
    var ulSize = liSize * maximum;   
    var divSize = liSize * visible;  
 
    $('#my_carousel ul').css("width", ulSize+"px").css("left", -(current * liSize)).css("position", "absolute");
 
    $('#my_carousel').css("width", divSize+"px").css("height", carousel_height+"px").css("visibility", "visible").css("overflow", "hidden").css("position", "relative"); 
 
    $('.btnnext').click(function() { 
      if(current + step < 0 || current + step > maximum - visible) {return; }
      else {
        current = current + step;
        $('#my_carousel ul').animate({left: -(liSize * current)}, speed, null);
      }
      return false;
    });
 
    $('.btnprev').click(function() { 
      if(current - step < 0 || current - step > maximum - visible) {return; }
      else {
        current = current - step;
        $('#my_carousel ul').animate({left: -(liSize * current)}, speed, null);
      }
      return false;
    });
  });