index-css.html

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>test document</title>
  <link rel="stylesheet" href="styles-css.css">
</head>
<body>

  <h1>CSS-only popup thing</h1>

  <div id="info_1">
    <a href="#">x</a>
    some stuff 01
  </div>
  <a href="#info_1" class="button"></a>

  <div id="info_2">
    <a href="#">x</a>
    some stuff 02
  </div>
  <a href="#info_2" class="button"></a>
  
  <div id="info_3">
    <a href="#">x</a>
    some stuff 03
  </div>
  <a href="#info_3" class="button"></a>
  
</body>
</html>