Notifications Subscription Button
And a couple of other things regarding strings...
1- The same "Confirm your subscription" string is used for displaying a message to the user on the site after he subscribed, and in the mail for the text of the link to confirm. I would suggest that you use 2 different strings, so that a much more clear message can be displayed on the site (like "You will receive a mail allowing you to confirm your subscription").
2- "Subscription not successed" string is missing from the phrases settings in admin.