$(function() {
        $('#cat li > ul').each(function(i) {
            var parent_li = $(this).parent('li');
            var sub_ul = $(this).remove();
            parent_li.find('span').click(function() {
                sub_ul.toggle();
                if (this.innerHTML == '<img src="/images/plus.gif">') {
                    this.innerHTML = '<img src="/images/minus.gif">';
                } else if (this.innerHTML == '<img src="/images/minus.gif">') {
                    this.innerHTML = '<img src="/images/plus.gif">';
                }             
            });
            parent_li.append(sub_ul);
        });    
        $('ul ul.hide').hide();
    });