.main_menu {
  background-image:url(img/bgm_sso.gif);
}
.menu_home {
 background-image:url(img/bgm_sso_home.jpg);
}
.menu_leist {
 background-image:url(img/bgm_sso_leist.jpg);
}
.menu_ref {
 background-image:url(img/bgm_sso_ref.jpg);
}
.menu_mit {
 background-image:url(img/bgm_sso_mit.jpg);
}
.menu_uns {
 background-image:url(img/bgm_sso_uns.jpg);
}
.menu_kont {
 background-image:url(img/bgm_sso_kont.jpg);
}