If you’re writing copy for a website, you can’t use the same principles as when writing for a print publication.
Documents written to be read online must be concise and structured for scanning. People tend to skim Web pages rather than read them word by word. Use headings, lists, and typographical emphasis for words or sections you wish to highlight; these are the elements that will grab the user’s attention during a quick scan. Keep these elements clear and precise â€” use your page and section heads to describe the material. The “inverted pyramid” style used in journalism works well on Web pages, with the conclusion appearing at the beginning of a text. Place the important facts near the top of the first paragraph where users can find them quickly.
From: The Web Style Guide
This is not a new topic by any means, but one that bears reiterating.
So, to get you on the path to writing succinctly for the web, here are some useful links:
Organizing your prose
How to Write for the Web
Downloadable Files to Replicate Web-Reading Study
Inverted Pyramids in Cyberspace
How people read on the web