var scrollerSemafor = false;
var viewportWidth   = 510;
var animationDuration = 500;

  $('document').ready( function() 
  {
    $('#imagesLeft').click( imagesLeft );
    $('#imagesRight').click( imagesRight );
  });


  function imagesLeft()
  {
    if (!scrollerSemafor) {
      scrollerSemafor = true;
      var columns = $('#imagesContainer');
      var last  = $(columns).children('li:last');
      var clone = $(last).clone();
      $(last).remove();
      $(columns).css('marginLeft', parseInt($(columns).css('marginLeft')) - viewportWidth + 'px').prepend($(clone));
      $(columns).animate({
        marginLeft: '+=' + viewportWidth +'px'
      }, animationDuration);
      setTimeout(function()
      {
        scrollerSemafor = false;
      }, animationDuration + 100);
    }

  }

  function imagesRight()
  {
    if (!scrollerSemafor) {
      scrollerSemafor = true;
      var columns = $('#imagesContainer');
      $(columns).animate({
        marginLeft: '-=' + parseInt(viewportWidth + 2) +'px'
      }, animationDuration);
      setTimeout(function()
      {
        var first = $(columns).children('li')[0];
        var clone = $(first).clone();
        $(first).remove();
        $(columns).css('marginLeft', parseInt($(columns).css('marginLeft')) + parseInt(viewportWidth + 2) + 'px').append($(clone));
        scrollerSemafor = false;
      }, animationDuration + 100);
    }
  }