Confluence allows public (anonymous) viewing/access to spaces and pages. For various reasons one might want to disable various elements on a space or page.
The above example also hides certain elements for including the quick search panel and help-menu.
You'll notice that you can also set specific element CSS just for anonymous users (see line 9).
- Atlassian's guide to custom HTML here
- Atlassian's excellent page for hiding elements via CSS or JS here (includes list of selector names)