<!DOCTYPE html> <html class="reftest-wait"> <head> <style> .outer { transform-style: preserve-3d; width: 200px; height: 200px; } .inner { top: 50%; transform: translateY(-50%); background-color: green; position:relative; width: 200px; height: 200px; } </style> </head> <body> <div id="outer" class="outer"> <div class="inner"> </div> </div> <script> function doTest() { document.getElementById("outer").style.opacity = 0.7; document.documentElement.removeAttribute("class"); } window.addEventListener("MozReftestInvalidate", doTest, false); </script> </body> </html>