This page tests whether an X-content-age: 18 header is respected if specified in an age.xml file.
If you are seeing this page, your current setup does not block content labelled in this way.
The X-content-age header can be used as part of the age.xml labelling system to apply an age rating to specific parts of a site.
Note: This test is only expected to work in conjunction with a correspong age.xml file in the root of the server, so it is not contained within this HTML file alone.