对象不支持此属性或方法“同位素”

我的网站有问题。我在IE8/9上收到网页错误：

对象不支持此属性或方法 "同位素" 行： 47 字符： 3 代码： 0

代码如下：

/*-----------------------------------------------------------------------------------
/*
/* Custom JS
 /*
-----------------------------------------------------------------------------------*/
/* Start Document */
jQuery(document).ready(function($) {
/*----------------------------------------------------*/
/*  Responsive Menu
/*----------------------------------------------------*/
      // Create the dropdown bases
      $("<select />").appendTo("#navigation");
      // Create default option "Go to..."
      $("<option />", {
         "selected": "selected",
         "value"   : "",
         "text"    : "Menu"
      }).appendTo("#navigation select");

      // Populate dropdowns with the first menu items
      $("#navigation li a").each(function() {
        var el = $(this);
        $("<option />", {
            "value"   : el.attr("href"),
            "text"    : el.text()
        }).appendTo("#navigation select");
      });

      //make responsive dropdown menu actually work     
        $("#navigation select").change(function() {
            window.location = $(this).find("option:selected").val();
        });
/*----------------------------------------------------*/
/*  Isotope Portfolio Filter
/*----------------------------------------------------*/
  $(function() {
    var $container = $('#portfolio-wrapper');
    // initialize Isotope
    $container.isotope({
      // options...
      resizable: false, // disable normal resizing
      // set columnWidth to a percentage of container width
      masonry: { columnWidth: $container.width() / 12 }
    });
    // update columnWidth on window resize
    $(window).smartresize(function(){
      $container.isotope({
      // update columnWidth to a percentage of container width
      masonry: { columnWidth: $container.width() / 12 }
      });
    });

      $container.isotope({
        itemSelector : '.portfolio-item'
      });
      var $optionSets = $('#filters .option-set'),
          $optionLinks = $optionSets.find('a');
      $optionLinks.click(function(){
        var $this = $(this);
        // don't proceed if already selected
        if ( $this.hasClass('selected') ) {
          return false;
        }
        var $optionSet = $this.parents('.option-set');
        $optionSet.find('.selected').removeClass('selected');
        $this.addClass('selected');
        // make option object dynamically, i.e. { filter: '.my-filter-class' }
        var options = {},
            key = $optionSet.attr('data-option-key'),
            value = $this.attr('data-option-value');
        // parse 'false' as false boolean
        value = value === 'false' ? false : value;
        options[ key ] = value;
        if ( key === 'layoutMode' && typeof changeLayoutMode === 'function' ) {
          // changes in layout modes need extra logic
          changeLayoutMode( $this, options )
        } else {
          // otherwise, apply new options
          $container.isotope( options );
        }
        return false;
      });
});
/*----------------------------------------------------*/
/*  Back To Top Button
/*----------------------------------------------------*/
    var pxShow = 300;//height on which the button will show
    var fadeInTime = 400;//how slow/fast you want the button to show
    var fadeOutTime = 400;//how slow/fast you want the button to hide
    var scrollSpeed = 400;//how slow/fast you want the button to scroll to top. can be a value, 'slow', 'normal' or 'fast'
    jQuery(window).scroll(function(){
      if(jQuery(window).scrollTop() >= pxShow){
        jQuery("#backtotop").fadeIn(fadeInTime);
      }else{
        jQuery("#backtotop").fadeOut(fadeOutTime);
      }
    });
    jQuery('#backtotop a').click(function(){
      jQuery('html, body').animate({scrollTop:0}, scrollSpeed); 
      return false; 
    }); 
/* End Document */
})();

怎么了？