JSFiddle - React, Tailwind, and code Playground

HTML

<body>
    <header>
      <nav>
        <ul>
          <li><a href="">Num1</a></li>
          <li><a href="">Num2</a></li>
        </ul>
      </nav>
    </header>
  </body>

CSS

body, html {padding: 0; margin: 0;}
header {
  margin: 0;
  padding: 0;
  background: #0e83cd;
}
nav ul {
    margin: 0;
  display: block;
  list-style: none;
}
nav ul li {
  display: inline;
}
nav ul li a {
  display: inline;
}