slidetoggle doesn't use css about jquery-animate-enhanced HOT 2 CLOSED

<div class="target">
            Content to slide
</div>
<button id="start">Run test</button>
<script>
$('button#start').click(function() {
                    button = $(this).attr('disabled', 'disabled');
                    $('.target').slideToggle(1000, function() {
                            $('.target').slideToggle(1000, function() {
                                    button.removeAttr('disabled');
                            });
                    });
            });
</script>