CHAPTER 43. CH42 ELEMENTS OF HTML 328
it is not the main content.
Theasidetag (semantic) is likediv, identifies “by the way” content that is
a deeper view of something that is only tangential to the main flow of the
webpage.
43.2.2 Headings
Theh1tag (structural) identifies a top-level header.
Theh2tag (structural) identifies a second-level header, and implies a child
relationship to the previoush1tag.