#menu-item-457155 a { 
  background: transparent url(/obrazek/3/sk/) no-repeat center; 
  width: 42px;
  font-size: 0;
  line-height: 26px;
  opacity: 0.6;
}
#menu-item-457155 a:hover { 
  background: transparent url(/obrazek/3/sk/) no-repeat center;
  opacity: 1;
}