<html xmlns="http://www.w3.org/1999/xhtml" xmlns:xbl="http://www.mozilla.org/xbl"> <head> <style> .forced { display:block; } </style> </head> <body> <xbl:children> FAIL </xbl:children> <xbl:children class="forced"> FAIL </xbl:children> <xbl:children /> <script> var third = document.body.children[2]; third.appendChild(document.createTextNode("FAIL")); var fourth = document.createElementNS("http://www.mozilla.org/xbl", "children"); fourth.appendChild(document.createTextNode("FAIL")); document.body.appendChild(fourth); </script> </body> </html>