var $ul = $('ul');
if($ul.find("li").length > 2 && $ul.find('.active, .inactive').length  == 2) {
       alert('yes, it is this way');
}​

<ul>
  <li class="active">Whatever</li>
  <li class="inactive">Whatever</li>
  <li>Whatever</li>
  <li>Whatever</li>
</ul>​

演示: http://jsfiddle.net/RtTSM/1/