The alert is a simple colored block meant to draw the attention to the user about something. They persist until the message is resolved or dismissed by user.
Alert status helps convey the information being communicated. These statuses correspond with a color and icon to provide a consistent, universal experience for users. They come in 4 status:
Alerts do not dismiss automatically. They persist on the page until the user dismisses them or takes action that resolves the notification.
Including the close button is optional and should not be included if it is critical for a user to read or interact with the notification.