Presumably, you're using Firefox or Safari, and so the `initial-letter` CSS property they're trying to use to make a big serif 'R' dropcap letter is breaking: https://developer.mozilla.org/en-US/docs/Web/CSS/initial-let...

(You're not missing much. 'A large serif letter from the body font' is about the most boring possible dropcap and not really worth the hassle, IMO.)