Please don't write off somebody's lack of attention to typography as a virtue and clever design. It's not. Browsers display it how they are told to display it. Maybe your system could use better fonts or line spacing by default, it's arguable, but it definitely would be stupid and unreasonable for browser to enforce less than maximal width for some of your div's if not told otherwise. If anything, they already enforce more than they should (that's why normalize.css exists).

And, by the way, it's not like there's no css at all in the source. It's just UX-ignorant, so to say.

Browser defaults have a legacy and they're not easy to change without disruption. Just because they're less than ideal isn't an valid excuse to neglect your content presentation.

The author seems to have concerns for UX because his page isn't just HTML. He put some CSS on the nav header, used some HTML5 semantic elements, some Aria roles, and added a viewport header element for mobile scaling. Sadly his concerns were passing as 1/3 of his CSS is rendered moot, and his desire for a semantic page was abandoned quickly after implementing his navigation and footer.

His page's UX is improved dramatically by adding 2 simple CSS rules (margin, max-width). If those rules add too many bytes to the page he could convert his navigation divs to a proper unorder list and get some bytes back and make his page more semantic to boot.

His page is just a drive by attempt at standards and it's lazy.

Or an example of someone being too damn lazy to put effort into their offerings. I wouldn't be saying anything except that it takes so little effort to make it 1000x more readable than he did.

http://bettermotherfuckingwebsite.com/