@media screen and (max-width: 999px)
                {
                    div.kopf        {   display: none;}
                }

@media screen and (min-width: 1000px)
                {
                    div.kopf        {   display:block;}
                }


div.kopf img    {   width: 1000px; height: 170px; 
                    display: block; margin: auto; /*Display block bei Bildern, damit margin auto funktioniert*/
                }

aside           {   position: fixed;
                    top: 50%; right: 10%;
                    list-style: none;}