ul {
  list-style: none;
  font-size: 0;
  padding: 0;
  margin: 0;
  text-align: center;
}

ul li{
  display: inline-block;
}

ul li a {
  color: #000;
  text-decoration: none;
  font-size: 20px;
  font-family: Arial, Helvetica, sans-serif;
  padding: 10px;
  margin: 10px;
  border-width: 2px;
  border-style:solid;
  border-color: white;
  color: white;
  background-color: blueviolet;
}