You have the option to add the alert bar to the top of your site. You can edit this by going to Content > Link Lists > Alert Bar in the CMS.

The title will display first in the alert, and the description field controls the text. The link field controls where the alert bar links to.

To turn the alert off, change the name of the link list to "Alert Bar - Off". To turn it back on, change it back to "Alert Bar"