jQuery Tab 怎么自动切换啊

        <script src="http://code.jquery.com/jquery-latest.js"></script>
<SCRIPT language=javascript type=text/javascript>
$(document).ready(function () {   
$('.tabtitle li').click(function () {
var index = $(this).index();
$(this).attr('class',"tabhover").siblings('li').attr('class','taba');
$('.tabcontent').eq(index).show(200).siblings('.tabcontent').hide();
});
    var t = 0;
    var timer = setInterval(function(){
        if( t == $('.tabtitle li').length ) t = 0;
        $('.tabtitle li:eq('+t+')').click();
        t++;
    }, 700)
})
</SCRIPT>


<div class="maintab">
<ul class="tabtitle">
<li class="tabhover"><a href="#">选择标题1</a></li>
  <li class="taba"><a href="#">选择标题2</a></li>
  <li class="taba"><a href="#">选择标题3</a></li>
  <li class="taba"><a href="#">选择标题4</a></li>
  <li class="taba"><a href="#">选择标题5</a></li>
</ul>

<div class="tabcontent">
选择内容1
</div>
<div class="tabcontent" style="DISPLAY: none">
选择内容2
</div>
<div class="tabcontent" style="DISPLAY: none">
选择内容3
</div>
<div class="tabcontent" style="DISPLAY: none">
选择内容4
</div>
<div class="tabcontent" style="DISPLAY: none">
选择内容5
</div>
</div>