$(document).ready(function(){
 
  activeItem = $("#accordion li a:first");
  $(activeItem).addClass('active');
 
  $("#accordion li a").click(function(){
      $(activeItem).animate({width: "40px"}, {duration:500, queue:false});
      $(this).animate({width: "600px"}, {duration:500, queue:false});
      activeItem = this;
  });
 
});