css/css-pseudo/first-line-opacity-001.html

<!DOCTYPE html>
<html>
<head>
<title>CSS Test: ::first-line supports opacity.</title>
<link rel="author" title="Mats Palmgren" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1639664">
<link rel="match" href="first-line-opacity-001-ref.html">
<link rel="help" href="https://drafts.csswg.org/css-pseudo-4/#first-line-styling">
  <style>
    p::first-line {
      opacity: 0;
    }
  </style>
</head>
<body>
  <p>First<br>Second</p>
</body>
</html>