<!DOCTYPE html> <html class="reftest-wait"> <head> <style type="text/css"> .separator { height: 20px; background-color: green; } </style> <script type="text/javascript"> function test() { document.getElementById('margin-only').style.margin = '20px 0 10px'; document.documentElement.removeAttribute('class'); } document.addEventListener('MozReftestInvalidate', test, false); </script> </head> <body> <div class="separator"></div> <div id="margin-only"></div> <div class="separator"></div> </body> </html>