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  <pre data-lang="html">&lt;h1>Hello from HTML&lt;/h1></pre>
  <pre data-lang="css">html {
  background: black;
  color: white;
  text-align: center;
}

h1::after {
  content: " / CSS!";
}
</pre>
  <pre data-lang="js">document.querySelector("h1").innerText += " / JavaScript";
</pre>
</div>
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