index.html

<!DOCTYPE html>
<html lang="pt-Br">
<head>
    <meta charset="UTF-8">
    <meta name="keywords" content="your tags" />
    <meta name="description" content="150 words" />
    <meta name="subject" content="your website's subject">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="style.css">
    <title>xxxx</title>
    
</head>
<body>
    <header>
        <h1>PetShop 007</h1>
        <h2>Seu bichinho bem cuidado</h2>
    </header>    
    <nav id="navbar">
        <ul>
            <li>
            <a href="#a" id="linka" class="xx">Link A</a>
         </li>
         <li>
            <a href="#b">Link B</a>
            </li>
        </ul>
    </nav>
    <main id="app">
        <article>
            <section class="secao"></section>
            <section class="secao"></section>
            <section class="secao"></section>
        </article>
        <aside>

        </aside>
    </main>
    <footer>
        <nav>

        </nav>
    </footer>
</body>
</html>