HTML and CSS Reference
h1, h2, h3, h4, h5, h6
<h n > . . . </h n >
Specifies a heading that briefly describes the section it introduces. There are six levels of
headings, from h1 (most important) to h6 (least important). HTML syntax requires that head-
ings appear in order (for example, an h2 should not precede an h1 ) for proper document struc-
ture. Doing so not only improves accessibility, but aids in search engine optimization (inform-
ation in higher heading levels is given more weight).
In HTML5, heading order can be repeated within sections of the same document, allowing
greater flexibility with heading levels. This is to aid the outlining of documents and allows
sections of a document to fall into the outline correctly no matter which document the section
appears in. The HTML5 outline algorithm is not well supported as of this writing.
Flow content, heading content, palpable content
Where flow content is expected