Above is a script library.
If you install this library script, WebMail Notifier will become 'Web Update Notifier'.
You can check the update of webpage with WebMail Notifier.
But this script does not work alone.
This script is for monitoring AMO.
You can check a new post in addons.mozilla.org
Install these two script. Then you will see the host name 'AMO' in the list.
Make a account.
Set username as the name of addon.
Set password as the addon number.(you can see the number in the url of addon.)
Now you can see the notificatio of WebMail Notifier when there is a new posting in AMO.