Should "et al." be written in italics, or not?
My impression was that it was, but http://www.ece.ucdavis.edu/~jowens/commonerrors.html and http://blog.apastyle.org/apastyle/2011/02/et-al-when-and-how.html says it should not be italicised, but I previously thought it should be, as does this side-remark in this answer.