Sortable doesn't work
<p>I have a problem. I would like to be able to sort the list. I made this script, but "sortable" doesn't work. Why?</p>

<pre><code>&lt;html&gt;
&lt;script type="text/javascript"&gt;
        var count = 1;
        $(function(){
            $('#add_item').click(function(){
                count++;
                $('#container').append('&lt;li id="item_' + count +'"&gt;' + count + '° posto: '+ '&lt;input type="text" id="item_' + count + '" name="items[]" type="text" /&gt;&lt;input type="submit" class="del_item" value="Elimina" /&gt;&lt;br /&gt;&lt;/li&gt;');
                return false;
            });
            $('form').on('click', '.del_item', function(){
                count--;
                $(this).parent().remove();
                return false;
            });
            $('#container').sortable();
        });
    &lt;/script&gt;


&lt;ul id="container"&gt;
            &lt;li id="item_1"&gt;1° posto: &lt;input type="text" id="item_1" name="items[]" /&gt;
            &lt;input type="submit" class="del_item" value="Elimina" /&gt;&lt;br /&gt;&lt;/li&gt;
        &lt;/ul&gt;
        &lt;input type="submit" name="add_item" id="add_item" value="Aggiungi" /&gt;&lt;br /&gt;

&lt;/html&gt;
</code></pre>

<p>Could you help me, please?</p>
