css/css-position/position-sticky-table-th-top-ref.html

<!DOCTYPE html>
<title>Reference for position:sticky top constraint should behave correctly for &lt;th&gt; elements</title>

<style>
.group {
  display: inline-block;
  position: relative;
  width: 150px;
  height: 200px;
}

.scroller {
  position: relative;
  width: 100px;
  height: 150px;
  overflow-x: hidden;
  overflow-y: auto;
}

.contents {
  height: 550px;
}

.indicator {
  position: absolute;
  background-color: green;
  left: 0;
  height: 50px;
  width: 50px;
}
</style>

<script>
window.addEventListener('load', function() {
  document.getElementById('scroller1').scrollTop = 50;
  document.getElementById('scroller2').scrollTop = 125;
  document.getElementById('scroller3').scrollTop = 250;
});
</script>

<div class="group">
  <div id="scroller1" class="scroller">
    <div class="indicator" style="top: 100px;"></div>
    <div class="contents"></div>
  </div>
</div>

<div class="group">
  <div id="scroller2" class="scroller">
    <div class="indicator" style="top: 150px;"></div>
    <div class="contents"></div>
  </div>
</div>

<div class="group">
  <div id="scroller3" class="scroller">
    <div class="indicator" style="top: 250px;"></div>
    <div class="contents"></div>
  </div>
</div>

<div>You should see three green boxes above. No red should be visible.</div>