People scan web pages before they decide to read them. Clear web writing respects that.
Put the main point first, then support it. Readers should never have to hunt for what you mean.
Use short sentences with one idea in each, and short paragraphs with one topic in each.
Write headings that say something. A reader skimming only the headings should still understand the page.
Read your work aloud before publishing. If you run out of breath, the sentence is too long.