palemoon-dev/platform/layout/reftests/first-letter/overflow-float-overflow.html

<title>::first-letter and overflow</title>
<style>

div {
  height: 3em; width: 8em;
  padding: 3px;
  background: yellow; color: black;
  overflow: auto;
  line-height: 1.0;
}
div::first-letter { font-size: 4em; float: left; }

</style>

<div>Hello</div>