<!DOCTYPE HTML> <html class="reftest-wait"> <body> <div style="-moz-column-count:2; column-count:2; width:300px; height:100px;"> <div id="o" style="opacity:0.5; width:100px; height:200px; background:lime;"> <div id="d" style="height:50px; width:80px; background:red; padding:2px">Text</div> </div> </div> <script> var o = document.getElementById("o"); var d = document.getElementById("d"); document.body.getBoundingClientRect(); o.style.opacity = 0.8; function doTest() { o.style.opacity = 0.9; document.body.getBoundingClientRect(); d.style.background = "green"; document.documentElement.removeAttribute("class"); } window.addEventListener("MozReftestInvalidate", doTest, false); </script> </body> </html>