<html><head> <style> div { outline: 1px solid black; } </style> </head><body> You should see no red, only green<br> <div style="overflow: scroll; height: 200px; z-index: 2; position: relative; background-color: red;"></div> <div class="displayport" reftest-displayport-h="500" style="overflow: scroll; position: relative; margin-top: -200px; height: 200px;"> <div style="z-index: 10; position: absolute; width: 100%; height: 500px; bottom: -300px;"> <div style="height: 200px; background-color: lime;"></div> </div> </div> </body></html>