2.2.28 [HTML] Section 16.1, Introduction to frames


The specification states:

 If the user agent can't display frames or is configured not to, it will render the 
 contents of the NOFRAMES element.

All Document Modes (All Versions)

Frameset content is blocked for sites that belong to the Restricted sites zone. When this is the case, content in the NOFRAMES element is also ignored.