header {
  background: #333;
}

ul:first-child {
  margin-left: 0;
  padding-left:0;
  /* warum ist da so viel Abstand nach rechts */
}

ul{
  float:left;
  display:block;
}

li {
  display: inline;
  padding:0px;
  margin:0px;
}

a {
  color: white;
  text-decoration: none;
  background: #999;
  padding: 14px 16px;
  display:inline-block;
}

a:hover {
  background: #ffff66;
  color: black;
}