index.html

<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>CSS Navigation Bar</title>
    <style>
        :root{
            --color: yellow;
            --background-color:red;
            --box-color:yellowgreen;
            --seccolor:grey;
        }
        * {
            margin: 3px;
            padding: 2px;
            background-color: var(--color);
        }

        ul {
            display: flex;
            list-style: none;
        }

        li {
            padding: 3px;
            margin: 4px;
            color: var(--seccolor);
            font-weight: bold;
            font-size: 17px;
        }

        
    </style>
</head>

<body>
    <header>
        <nav>
            <ul>
                <li>Home</li>
                <li>About</li>
                <li>Contact</li>
                <li>Infosys</li>
            </ul>
        </nav>
    </header>
</body>

</html>