Indeed, I spotted a couple of typos too: "This book is free/libé", "to provide detaile information".

Also noticed that foreground colors are defined in the HTML version, while the background color isn't, and the blockquote foreground color doesn't meet the AAA level of WCAG contrast guidelines even if white background is assumed. That's rather nitpicky, and generally it's fine, but it feels like materials on UI and UX should better follow common guidelines.

Thanks! I pushed a version without the typos and slightly more contrasting colors, including a defined background color.

Ohno, “reserach” is my favorite spelling mistake. I regularly search-replace for it and regularly create new reseraches.