How to detect tumblr unfollowers!

1. These are the complete installation instructions. You first need to download and install the GreaseMonkey add-on. It works in almost any browser outthere, Internet Explorer, Firefox, Chrome, Opera and Safari.
2. Download Tumblr Unfollow Tracker script.
3. Always position your cursor over the followers counter to actually see the ? symbol and click on it to pop up the window that lest you see the people who unfollowed you.

Notes.

1. It only detects unfollows after it is installed, not prior to it.
2. A Tumblr username change or a deleted account will also be interpreted as an unfollow.
3. If a user follows and then unfollows during last time you checked and before you check again, it won’t show.

(Source)

Another way to detect unfollowers is through the website called "OpenInferno":

• TumblrStalk

It lets you trace your unfollowers by logging into the site with your tumblr email and password:)