*{
  margin:0;
  padding:0;
  font-family: century gothic;
}
header{
  background-image: url('a.jpg');
  height: 100px;
  background-size:cover;
  background-position: center;
  text-align : center;
}
ul{
  float:left;
  list-style-type:none;
  margin:top;
}
ul li{
  display:inline-block;
}
ul li a{
  text-decoration:none;
  color:#fff;
  padding: 5px 20px;
  border:1px solid #fff;
  transition:0.6 ease;

}
ul li a:hover{
  background-color:#fff;
  color:#000;
}