#menu a.welcome {
  background-image: url(/gui/menu-welkom.gif);
}
#menu a.welcome:hover {
  background-image: url(/gui/menu-welkom_a.gif);
}
#menu a.showcase {
  background-image: url(/gui/menu-portfolio.gif);
}
#menu a.showcase:hover {
  background-image: url(/gui/menu-portfolio_a.gif);
}
#menu a.contact {
  background-image: url(/gui/menu-contactgegevens.gif);
}
#menu a.contact:hover {
  background-image: url(/gui/menu-contactgegevens_a.gif);
}