I have created reponsive design given in assesment link : https://developer.mozilla.org/en-US/docs/Learn/CSS/CSS_layout/rwd_skills . i have problem in styling header

<meta charset="utf-8" />

<title>Responsive Web Design Task: Task</title>

<link rel="stylesheet" href="css/RD1.css" />

<meta name="viewport" content="width=device-width, initial-scale=1" />

<style>

  * {

    box-sizing: border-box;

  }

  html {

    font: 1.2em/1.4 Arial, Helvetica, sans-serif;

  }

  body {

    padding: 0 0 1em;

  }

  header {

    background-color: #333;

    color: #fff;

    border: 5px solid #000;

  }

  header ul {

    list-style: none;

    margin: 0;

    padding: 0;

  }

  header a {

    color: #fff;

    text-decoration: none;

    display: block;

    padding: 0.5em 1em;

    border-top: 1px solid #999;

  }

  header .title {

    font-size: 150%;

    font-style: italic;

    font-weight: bold;

    padding: 1em;

  }

  main {

    padding: 0 1em;

  }

  .cards {

    list-style: none;

    margin: 0;

    padding: 0;

  }

  .cards li {

    border: 5px solid #000;

    margin-bottom: 1em;

  }

  .cards h2 {

    background-color: #333;

    color: #fff;

    margin: 0;

    padding: 0.5em 1em;

  }

  .cards .inner {

    padding: 0.5em 1em;

  }

  .sidebar {

    background-color: #333;

    border: 5px solid #000;

    padding: 0.5em 1em;

    color: #fff;

  }

  @media screen and (min-width: 70em) {

    body {

      display: grid;

      grid-template-rows: 100px 1fr;

      gap: 1em;

    }

    header {

      display: grid;

      grid-template-columns: 3fr 1fr;

    }

    header ul {

      display: grid;

      grid-template-columns: 1fr 1fr 1fr;

    }

    main {

      display: grid;

      grid-template-columns: 2fr 1fr;

      gap: 3em;

    }

    .cards {

      display: grid;

      grid-template-columns: 1fr 1fr 1fr;

      gap: 1em;

    }

  }

</style>
<header>

  <div class="title">My Website</div>

  <nav>

    <ul>

      <li>

        <a href="">Link 1</a>

      </li>

      <li>

        <a href="">Link 2</a>

      </li>

      <li>

        <a href="">Link 3</a>

      </li>

    </ul>

  </nav>

</header>

<main>

  <article>

    <h1>This is the main heading</h1>

    <p>

      Veggies es bonus vobis, proinde vos postulo essum magis kohlrabi welsh

      onion daikon amaranth tatsoi tomatillo melon azuki bean garlic.

    </p>

    <p>

      Gumbo beet greens corn soko endive gumbo gourd. Parsley shallot

      courgette tatsoi pea sprouts fava bean collard greens dandelion okra

      wakame tomato. Dandelion cucumber earthnut pea peanut soko zucchini.

    </p>

    <ul class="cards">

      <li>

        <h2>Card One</h2>

        <div class="inner">

          <p>

            Turnip greens yarrow ricebean rutabaga endive cauliflower sea

            lettuce kohlrabi amaranth water spinach avocado.

          </p>

        </div>

      </li>

      <li>

        <h2>Card Two</h2>

        <div class="inner">

          <p>

            Daikon napa cabbage asparagus winter purslane kale. Celery

            potato scallion desert raisin horseradish spinach carrot soko.

          </p>

        </div>

      </li>

      <li>

        <h2>Card Three</h2>

        <div class="inner">

          <p>

            Lotus root water spinach fennel kombu maize bamboo shoot green

            bean swiss chard seakale pumpkin onion chickpea gram corn pea.

          </p>

        </div>

      </li>

      <li>

        <h2>Card Four</h2>

        <div class="inner">

          <p>

            Lotus root water spinach fennel kombu maize bamboo shoot green

            bean swiss chard seakale pumpkin onion chickpea gram corn pea.

          </p>

        </div>

      </li>

      <li>

        <h2>Card Five</h2>

        <div class="inner">

          <p>

            Nori grape silver beet broccoli kombu beet greens fava bean

            potato quandong celery. Bunya nuts black-eyed pea prairie turnip

            leek lentil turnip greens parsnip.

          </p>

        </div>

      </li>

    </ul>

  </article>

  <aside class="sidebar">

    <p>

      Have you discovered all of the other excellent content on this

      website?

    </p>

  </aside>

</main>

Hi @anshul_rawat and welcome to the community :wave:

Your main and .cards grids look fine.
Try removing the body grid and changing header and header ul to flex.

Let me know if you need more help or if I shall look at an updated solution. :slightly_smiling_face:

Have a nice day,
Michael