header { width:100%; background-color:black;margin:0px;padding:0px;height:auto; }

nav { width: 100%;  margin: 0px; padding: 0px; position: absolute; top:210px; }
nav ul { text-align: center; padding: 0px; margin: 0px;}
nav li { float:left; width:20%; list-style: none; margin: 0px; padding: 0px; }
/* Unternavigation ausblenden */
nav ul ul { display: none; visibility: hidden; margin: 0px; padding: 0px; z-index: -1; }
/*  Unternavigation einblenden */
nav ul li:hover ul { display: block; visibility: visible; z-index: 999; opacity: 0.8; }
nav ul ul li { float: none; width:100%; }
nav a, nav span { color: white; background-color: green; display: block;
                text-decoration: none; line-height:50px;
                                /* Breite den in li enthaltenen Elementen zuweisen */
                                 }

nav uv ul ul a, nav ul ul span { }
/* aktuelle Unterseite kennzeichnen */
nav a:focus, nav a:hover, nav span { color: black; background-color: white; }
nav a:focus, nav a:hover { }
nav ul ul a:hover { }

footer { background-color:black; height:35px; }