$(document).ready(function() {
   function equalHeight(group) {
      tallest = 0;
       group.each(function() {
          thisHeight = $(this).height();
          if(thisHeight > tallest) {
             tallest = thisHeight;
          }
       });
      group.height(tallest);
   }
   // how to use
   $(document).ready(function() {
      equalHeight($(".left"));
      equalHeight($(".right"));
   });
});