Help Section - Invalid Data
What it means?
Sometimes you might view the people who unfollowed you by clicking on the users profile to view it on the Twitter website, but upon visiting Twitter still shows the user as following you.
Reason for this : Your PC, Phone or Tablet has cached an old page
When you visit web pages your device may store old versions of the page to speed up viewing them in future. This is known as caching, so when you check if the user has unfollowed/followed etc it will still show the user as following/not following you.
To Fix this issue
Just simply press the refresh button on the users profile page a few times, and it will show the live current data about whether the user is following you or not. When asked about incorrect data this is usually the reason why people get confused.
EXAMPLE 1 : Showing Cached Version of a user that doesn't follow you from twitter.com.
EXAMPLE 2 : Showing page after refreshing the web page from twitter.com.