Levels of Headings
2.8.1 Levels of Headings
A consistent style or typeface should be used for each level of heading throughout a manuscript so that the reader may visually distinguish between primary and secondary headings.
The styles used for the various levels of headings will vary from publisher to publisher and publication to publication, even within the same publishing house. They may also vary within a single publication, from one category of article to another (see also 22.0, Typography).
Headings are often used as navigational links for online articles. Consideration should be given to appropriate online use (eg, avoidance of excessive length and citation of images and references within headings).