iframe element Defines an inline frame (ie a frame embedded in a document), hgroup element The HTML Headings Group Element (<hgroup>) represents the heading of a section, command element The command element represents a command which the user can invoke. These elements allows child elements from interactive, embedded, heading, sectioning, phrasing, and metadata content categories.
Click the html element name in the punctuation list to advance the example in 'Tryit-Editor':