<!DOCTYPE html> <html class='reftest-wait'> <head> <style> :-moz-submit-invalid { display: none; } </style> </head> <script> function onloadHandler() { document.forms[0].appendChild(document.getElementById('b')); document.documentElement.className = ''; } </script> <body onload='onloadHandler();'> <button id='b' type='submit'></button> <form> <input required> </form> </body> </html>