Just to clarify the fact that this actually works with Firefox
(if you follow the link above it talks about mozilla browser).
You can change the user preferences in Firefox by
typing "about:config" into the navigation bar (or whatever
that thing is called where you type in an URL).
Query for "signed" and toggle the boolean to true (right mouse click on row).
Just mentioning this here, because it took me some time to figure this out.