User blog comment:Rupert Giles/Layout Changes: Breakpoints and Typography/@comment-13918697-20150527072158/@comment-452-20150529225648

I don't use the highlighting, so I'm not sure how it works, but I promise you that body { font-family: Arial, sans-serif; font-size: 10pt; line-height: 1.5em; } is valid CSS.

The .WikiaPage .WikiaArticle style overrides it in the content area, but it will still apply elsewhere.

edit: The CSS selector basics are
 * word by itself = tag name
 * . in front of a word = class name
 * # in front of a word = ID name