Fonction CSS element()

element(id)

<div id="boite-cible">
  <p>
    Cet lment utilise l'lment #mon-arriere-plan comme image de fond&nbsp;!
  </p>
</div>

<div id="conteneur-arriere-plan">
  <div id="mon-arriere-plan">
    <p>Et voici un texte inscrit sur l'arrire-plan.</p>
  </div>
</div>

#boite-cible {
  width: 400px;
  height: 400px;
  background: -moz-element(#mon-arriere-plan) no-repeat;
}

#conteneur-arriere-plan {
  overflow: hidden;
  height: 0;
}

#mon-arriere-plan {
  width: 1024px;
  height: 1024px;
  background-image: linear-gradient(to right, red, orange, yellow, white);
}

#mon-arriere-plan p {
  transform-origin: 0 0;
  rotate: 45deg;
  color: white;
}

<div id="css-source">
  <h1>Aperu de la page</h1>
</div>
<div id="css-result"></div>

#css-result {
  background: -moz-element(#css-source) no-repeat;
  width: 256px;
  height: 32px;
  background-size: 80%;
  border: dashed;
}