window.onload=function(){
   //cantonades
   $$('.top_box').each(
      function(p){
   		p.insert({bottom: '<span class="corner_top_left"></span><span class="corner_top_right"></span>'});
      });

   $$('.body_box').each(
      function(p){
   		p.insert({bottom: '</span><span class="corner_bottom_left"></span><span class="corner_bottom_right"></span>'});
      });
};