Gutenweb is a typographical stylesheet. It is a CSS file ready to use for quick document generation in html (and epub).
Gutenweb aims to forgot styling when marking-up a document, as you do when you generate a document in LaTeX. It is suitable for not too complex documents.
It adds some default styles which prioritize readability and they adapt to screen or print media. A lot of the concepts are taken from The Elements of Typographic Style Applied to the Web.