<!DOCTYPE html> <html class="reftest-wait"> <head> <style type="text/css"> #parent { width: 200px; background-color: lightgreen; } #inline-block1, #inline-block2 { height: 2em; width: 200px; background-color: green; vertical-align: bottom; } #inline-block1 { margin-bottom: 1em; } #inline-block2 { margin-top: 1em; } </style> <script type="text/javascript"> function test() { document.getElementById('inline-block1').style.display = 'inline-block'; document.getElementById('inline-block2').style.display = 'inline-block'; document.documentElement.removeAttribute('class'); } document.addEventListener('MozReftestInvalidate', test, false); </script> </head> <body> <div id="parent"> <div id="inline-block1"></div> <div id="inline-block2"></div> </div> </body> </html>