There are 2 sources worth visiting if you want to know more

Writing for the Web - a fantastic no nonsense site providing research on how users read on the Web and how authors should write their Web pages.

Suite 101.com - try this out for a short while. It costs nothing. Write 10 articles for them & by then your standard will have dramatically improved. Every article is rigorously reviewed by an editor.

I've been asked to give an example of a good article.

Well, I guess we ought to look in Suite 101.

Here's an article following all the principles laid out in this tutorial. It's been written by my wife (well it was one of the few by me actually, but don't tell anyone).

Ankle Injuries Advice and Treatment