The addon actually deteriorated in quality after the update to 4.0.2. The addon was pretty much perfect in my opinion until it was updated. It's worth mentioning that the reason the addon gets worse is because the author had to migrate to the web extension api. If you want to use this addon I really do suggest you use 3.5.23 available from here: https://addons.mozilla.org/en-GB/firefox/addon/xnotifier/versions/