<!DOCTYPE html> <!-- input in nested fieldset becomes barred --> <html class='reftest-wait'> <head> <style> fieldset:valid { background-color: green; } fieldset:invalid { background-color: red; } </style> </head> <script> function onloadHandler() { document.getElementById('i').readOnly = true; document.documentElement.className = ''; } </script> <body onload='onloadHandler();'> <fieldset> <fieldset> <input id='i' required> </fieldset> </fieldset> </body> </html>