Searching for information on a specific subject,
we hit the search term link and boom,
a full page of 10pt Times New Roman text appears.

First thought: back button.

Very few readers will endure an inefficient
web experience and will simply move on.
But, should everything we learned in
English & Marketing classes be thrown out?

Keep it short.  Don’t use 50 words to say what you can in 20.
Write for the reader’s goals (to get information), not the writer’s desires
(to sell, usually with too many words). Use short sentences, concise text &
avoid repetitive information.

Scannable text is key.   Website readers read differently than they do with
traditional writing or even email.  Research has shown that 79% of those tested
scanned any new page and only 16% read word-by-word (Morkes and Nielsen).
Use bullets, highlighted or bold text, white space, titles, lists, sub-headings,
summaries & short paragraphs to break up content.

Project credibility & sincerity with an active voice. The active voice is more straightforward, easier to understand & takes fewer words to write (and to read). Qualifiers dilute text - avoid should, may, might, etc.

Get to the point with the imperative voice.   
Begin the sentence with a verb and assume the subject “you.”

But wait, there’s more! If so, make it self-evident.
Hyperbole turns off visitors and reduces credibility.
Demonstrate with details, accurate examples, and customer testimonials.

Avoid changing verbs into nouns.   In linguistics, this practice is called nominalization
and is considered to make sentences more difficult to follow and promotes wordiness.

Consistency increases credibility. Conflicting terminology, naming & facts confuse
the reader and questions the site’s integrity & authority.
When facts change, make sure & change them everywhere on the website.