The site is simple to use, just sign in with Twitter via Oauth and then your off. Once logged in you can do the following tasks. You can manually check who has unfollowed you every 15 minutes, call out your unfollowers for unfollowing you, view people you are following that are not following you back and view a 7 day unfollower history.
Once you have checked who is not following you back on Twitter, you can then unfollow them, if you want to, or even post a tweet saying that tweeter isn’t following you any more.
(Details of this invaluable resource here.)
[This strikes me as very, very strange. I think Evan Soltas is very clever, for instance, so if he bothers to post on Twitter I would like to know, but I can't for the life of me see why he would want to follow me. If he were to do so on impulse he would soon discover his mistake. The idea that it would be rude of Mr Soltas not to follow me back, or that I might call out the hapless Mr Soltas for unfollowing me, seems completely ludicrous. Still, it's cheering to see that there is a whole miserable way of life out there that I have effortlessly avoided.]
[PS - Oh, er, yes, it is possible to follow me on Twitter. I am clearly not taking this seriously enough; otherwise I would presumably have been chivvying readers of pp into following me. (But, um, why?) Anyone who wants more ways to fritter away their time, though, would do better to follow Anatol Stefanowitsch (@astefanowitsch), who has a real genius for the medium.]