.only_if_logged_in{
    display: none !important;
}
.only_if_not_logged_in{
    display: none !important;
}
body.logged-in .only_if_logged_in{
    display: inline-block !important;
}
body:not(.logged-in) .only_if_not_logged_in{
    display: inline-block !important;
}