<!DOCTYPE html> <html class="reftest-wait"> <html> <head> <style type="text/css"> #abs-pos { top: 20px; left: 20px; width: 200px; background-color: lightgreen; } #in-flow-child { height: 100px; margin-top: 40px; margin-bottom: 40px; background-color: green; } </style> <script type="text/javascript"> function test() { document.getElementById('abs-pos').style.position = 'absolute'; document.documentElement.removeAttribute('class'); } document.addEventListener('MozReftestInvalidate', test); </script> </head> <body> <div id="abs-pos"> <div id="in-flow-child"></div> </div> </body> </html>