HTML/CSS components were not available to Guido in 1988. It was in 1989 that Tim Berners-Lee defined the first version of HTML[0] and CSS was proposed five years later[1]. In 1988 Guido would have known about the Mac (1984) which he cites, and the X Window system, which was 5 years old.[2]

[0] https://en.wikipedia.org/wiki/HTML#Development

[1] https://en.wikipedia.org/wiki/CSS#History

[2] https://en.wikipedia.org/wiki/X_Window_System#History