Editing With Multiple Authors
Blogs with multiple authors may have more than one person working on posts or pages at the same time. WordPress has a built in safe-guard from any conflicts this might cause. If you begin editing a post that someone else is working on, a warning will display at the top of the screen to let you know who is already editing that post.
If you see that another user is editing the post, it’s a good idea to exit the post screen immediately. Even if you make some changes and save them, if the other user does the same at a later time, your changes will be overwritten.