ul li{ 
  margin: 0;
  padding: 0;
}
#container {
  position: relative;
}

.menu-btn {
  width: 100px;

  color: #FFF;
  text-align: center;
  cursor: pointer;
  font-size: 13px; 
background: url(bk-top-menu-a.png) no-repeat center center; 
height:40px;
}
.menu-btn:hover {
  background: #000 url(bk-top-menu-h.png) no-repeat center center;
}