mozilla-release/layout/reftests/first-line/403177-1-ref.html

<html>
<head>
<style>

.fl:first-line { color: #ff00ff; background: #ffccff; }

.flWithContent:first-line { }

</style>
</head>

<body onload="document.getElementById('inner').removeAttribute('class');">

<div id="outer" class="fl">
  a
  <div id="inner" style="float: left;" class="flWithContent">
    b
  </div>
  c
</div>

</body>
</html>