gecko-dev/layout/reftests/css-animations/stacking-context-animation-...

<!DOCTYPE html>
<title>Reference of testcases for bug 1273042</title>
<style>
span {
  height: 100px;
  width: 100px;
  background: green;
  position: fixed;
  top: 50px;
  z-index: -1;
}
#test {
  height: 100px;
  width: 100px;
  background: blue;
}
</style>
<span></span>
<div id="test"></div>