css-flexbox-1/reference/negative-margins-001-ref.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>Reference for negative margins</title>
<style>
    .container {
        width: 60px;
        height: 10px;
        background-color: green;
        border: 3px black solid;
    }
</style>
<body>
    <p>You should see a green rectangle with a black border, 60px wide. You should see no red.</p>

    <div class="container">
        <div class="flex">
            <div class="item first"></div>
            <div class="item neg-marg"></div>
            <div class="item"></div>
        </div>
    </div>
</body>