.lavaLamp {
   height: 25px;
   margin: 0 auto;
   position: relative;
   }

.lavaLamp li {
   float: left;
   list-style: none;
   }
   
.lavaLamp li.back {
   height: 17px;
   width: 56px;
   margin-top: 47px;
   position: absolute;
   background: transparent url(../images/triangle_nav.png) no-repeat scroll center 0;
   }