// JavaScript Document by NetArt
 
$(document).ready(
    function () {
          $("ul.offer_list li").filter ( 
                        function (index) {                     
                             if ( index  % 3 == 0) {
                                $(this).addClass('list-clear');
                                return true;
                             }
                             return false;
                        }                           
                  );
   }
);