For security reasons, Salesforce logs off users after a period of inactivity. Users get a warning when their Salesforce session is about to expire and can choose to continue working. However, users didn’t see the warning if their Salesforce session was buried behind the current tab, so they were logged out without knowing it. Now, no more unfortunate surprises. When a user’s session is about to expire, a browser notification pops up in the foreground. This feature is new in Lightning Experience.
You can turn off Salesforce notifications from your browser.
Session notifications work on all browser versions supported byLightning Experience, except Internet Explorer version 11.