Remember the CMS acts as a library for its users. Files are checked out and checked in and can only be accessed by one user at a time.
When an item is checked out to someone who is not you, a lock (padlock) icon will be in place of a checkout (lightbulb) icon.
It might look something like this:
Who locked this page?
Hover over the lock to see who has checked out the file. You may either contact that individual to request he or she check in the file, or submit a request to Web & Digital Communications. Once the page has been checked in, it will be unlocked to you and you should be able to access the page.