This is a great guide that goes into exquisite detail but it is, unsurprisingly, not a great fit for the web. I lifted a few guidelines from the site (and added some detail) to give a better overview of what is most often overlooked and easily corrected in web typography. The ones I most wish would find a wide adoption:

There should be between about 45 and 75 characters in a single line. If there are not the user should at least be able to adjust the number of characters in a line.

Don’t justify without hyphenation. Never justify monospaced typefaces.

Use a single space between sentences.

Don’t letterspace lower case.

Pick an appropriate line height. The default is nearly always too small, especially for body text. Increase it but don’t break it.

Use the non-breaking space for mathematical and numerical expressions (like 4 cm).

Use hyphens, dashes and quotes correctly. (Not on the site and not a common mistake in the past but today it is everywhere.)

Does anyone else with a large monitor find that page difficult to read because of the dreadfully small font size?

That website is unchanged since at least 2006, probably 2004.

This is really neat, although still a work in progress. I'd thought about doing this for ages, at least for my own purposes, but now I see it like this I think he should open it up as a community effort, or at least encourage comments and contributions.

I cannot help but notice that this entire page uses serif fonts.

I'm not clear what your point is here. Perhaps you're referring to the common misapprehension that serif fonts are harder to read...

They could respect their own guidelines a little better but the content is great.