Occasionally Twitter will unfollow individual accounts. This could be for any one of the following reasons:
1. The account or person that you used to follow has been blocked (it may have been a bot). It may happen when you mass follow, especially at the beginning. For this reason, we strongly advise you to follow accounts which have a genuine profile picture.
2. The holder of the account has deleted his account.
3. The user you followed has blocked you. Click Follow on their profile. An error message means the user has blocked you from following them. This is very rare and again may be due to the original account being identified as spam.
On occasion, your account may show up as following 0 accounts.
This occurs when your account may have been temporarily blocked as you have been following/unfollowing too many accounts within a short period of time. This can result in automatically unfollowing all accounts on your list.
This is a temporary glitch and your follower numbers should return to normal shortly after you have verified your account.
Finally, if you find that your account is continually blocked by Twitter - as can happen when using follow/unfollow software - we advise you may need to reduce the number of actions you take on your account per day.
For further information following rules and best practices we encourage you to click the link here.