display-contents-block-002.html
<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Display: margin collapsing through display:contents</title>
<link rel="author" title="Rune Lillesveen" href="mailto:rune@opera.com">
<link rel="help" href="https://drafts.csswg.org/css-display-3/#valdef-display-contents">
<link rel="match" href="display-contents-block-002-ref.html">
<style>
#outer { margin-top: 100px }
#inner { margin-top: 300px }
#contents {
display: contents;
margin-top: 2000px
}
</style>
<p>You should see the word PASS with a 300px top margin below.</p>
<div id="outer">
<div id="contents">
<div id="inner">PASS</div>
</div>
</div>