css/css-backgrounds/background-attachment-margin-root-001.html

<!doctype HTML>
<title>Background-attachment: scroll should be positioned relative to the root element and should extend to cover the entire canvas in the presence of fixed backgrounds</title>
<link rel="author" title="Philip Rogers" href="mailto:pdr@chromium.org">
<link rel="help" href="https://www.w3.org/TR/css-backgrounds-3/#root-background">
<link rel="help" href="https://drafts.csswg.org/css-backgrounds-3/#the-background-attachment">
<link rel="match" href="background-attachment-margin-root-001-ref.html">
<style>
  html {
    background: linear-gradient(rgba(0,255,0,0.5), rgba(0,0,255,0.5)), linear-gradient(rgba(0,0,0,1), rgba(0,0,0,1));
    background-attachment: scroll, fixed;
    background-size: 100px 100px, 100px 100px;
    height: 300px;
    margin: 50px;
  }
</style>