#mainnav li.now a:hover img{margin:0;}

#mainnav li{float:left; position:relative;}
#mainnav a {float:left;display:block; height:29px; overflow:hidden;}
#mainnav a:hover img{margin-top:-29px;}

#mainnav li.display .dropmenu{ display:block;}
#mainnav li.hidden .dropmenu{ display:none;}

#mainnav .dropmenu { position:absolute; width:137px; top:29px; left:0;}
#mainnav .dropmenu li{clear:both;}
#mainnav .dropmenu a {display:block; height:28px; overflow:hidden;}
#mainnav .dropmenu a:hover img{margin-top:-28px;}