Writing for the web

Inverse correlation between text readability measures and success finding information on a web site. Less readability associated with authoritative, clear, complete, satisfying, useful. Why? Compare running prose with segmented text, like lists.
... Check readability at www.hp.com, an effective site.
Inverse correlation between white space and success finding information. Higher text density associated with ease of reading, ease of searching, overall appearance, ease of use, productivity. Why? Compare skimming with reading.
When writing is concise, objective, and scannable, studies showed 124-159% increase in usability measured by task time, errors, memory, time to recall, and satisfaction.

References:
Spool et al., Web site usability: A designer's guide, 1999.
Nielsen, Reading on the web, 1999.