Following this answer, I was able to insert some text with Firefox like thiscss\[code\]body{ -moz-binding: url(foo.xml#bar);}\[/code\]foo.xml\[code\]<bindings xmlns="http://www.mozilla.org/xbl"> <binding id="bar"> <content> Hello world </content> </binding></bindings>\[/code\]However I could not find a way to insert HTML rather text using this method.