We have a slightly interesting dilemma which is the result of some oddities in the APA style. Articles may have multiple levels of header in them, if they're divided into sections (both the articles I've worked on so far have two levels of header). APA, rather strangely, chooses to style headers based on the number of levels that happen to be present in the article; so, for example, where there are two or three levels, the second level is aligned left, but where there are four levels, the second level is centred, and the third level is left-aligned instead. For full details, see the APA Style Guide section 3.32.

Quite frankly, I think this is astoundingly silly, and so does everyone else I've shown it to. it means that the second level heading in one article may well be styled differently from the second level heading in another article. When we get to five levels, it gets even sillier; an ugly all-caps header is inserted at the top level, pushing all the other levels down, and making that particular article look radically different from others which use fewer levels of heading.

I've never really worked seriously with APA before, so this is new to me. Chicago and MLA seem to have nothing to say about it, other than Chicago's pragmatic assertion that levels of heading are "differentiated by type style and placement" (1.74). It makes for an interesting problem for XSLT and CSS, to say the least!