Writing in the digital realm, whether it’s writing on the web or writing e-mail or creating presentations, is in many ways quite like writing elsewhere; you still follow the same principles regarding grammar, usage, and style. In other ways, particularly those having to do with purpose, audience and delivery, writing in the digital realm is very different. This page links to various resources I’ve creating about writing for the Web, and writing HTML.
My opinions are my own and don't represent those of anyone else. Not that anyone would want them :)