When you receive notifications, the number of notifications will be indicated on your Global Navigation Bar.
Clicking the notification icon will show a notification summary.
You can go to the notification's designated Issue page by clicking the associated notification. If you are notified that you have been added to a Project, clicking the notification will bring you directly to the Project Home page.
The background indicates the status of the notification:
1 - Yellow: New
2 - Grey: Checked notification
3 -White: Unchecked notification
Please check here for details about Notifications.