Among your followers will be a wide range of fully automated, or computer aided Twitter accounts aiming to promote various products, directing you to adult websites, or trick you into parting with your passwords or credit card numbers.
If you want to detect and eliminate them from your account, there is a quick and easy way. TwitBlock is a free online service that offers an anti-junk filter and a blocking tool for Twitter users.
It lets you scan your Twitter account (required log-in) for detecting spammers and block them. And also you can analyze any account to determine whether it is spam or not.