Don’t underline any text that isn’t a link.
Italicize:
titles of books, movies, web series, magazines, newspapers, manuals, movies, television shows, and other full-length works, unless they're part of a link
words that require emphasis within your text
Letters as letters, words as words, and phrases as phrases (examples: “the o’s” “the word restart” “the phrase Welcome to the Library is used to...”
Use plain text and quotation marks for the titles of works that are more limited in scope, such as articles, stories, reports, TV episodes, podcast episodes, sections of blogs, songs, chapters and sections of works, and photographs.
Avoid the use of the ampersand except in article and page titles or when you are describing another entity or product that uses it in their name or title.
Bold text can be used in headings (if it is the default) and to bring attention to the most important parts of information, as demonstrated in this section of the style guide.
Don't use all-caps, except in official names that use them or in abbreviations and initialisms where appropriate.