So Michael Robertson has introduced AjaxWrite as a web-based word-processor. Nice idea, except what formats does it save to?
MS Word, RTF, Text and PDF.
How about HTML+CSS - it's how you're displaying the damn thing to me after all - how hard is it to store it in that format?
This is not a new question - after all CSS is more capable than Word's internal styling.
How about a Document Microformat? We can call it HTML for short.