• Use hierarchy to structure relations among information units.
• Use bullet lists instead of paragraphs.
• Use concise and factual sentences.
• Proofread everything twice!
• Update your pages frequently.
• Make sure all links are hot!
• Provide useful, specific information.
• Use bold text sparingly and use italics for emphasis.
• Avoid using “smart quotes” and auto hyphens.
• Avoid jargon and use terminology familiar to the user

Useful References

Writing for the Web by Jakob Nielson
http://www.sun.com/980713/webwriting/

Writing for the Web by Daniel Will-Harris
http://www.efuse.com/Design/web_writing_basics.html

10 Tips for Good Web Writing by Jennifer Kyrnin
http://webdesign.about.com/od/writing/a/aa031405.htm