<html xmlns="http://www.w3.org/1999/xhtml" xmlns:html="http://www.w3.org/1999/xhtml"> <head> <bindings xmlns="http://www.mozilla.org/xbl"> <binding id="foo" extends="html:input"> <content> Foo? <children/> </content> </binding> </bindings> </head> <body> <div>Hi!</div> <div style="-moz-binding: url(#foo)">XXX</div> </body> </html>