Body Text For reasons of density, I recommend that clients include no more than 450-600 words in total on each page (and ideally near the lower end of that range). If you need more words, then look at using more sections, categories, and pages. Remember your human readers. Do they want to read through 5,000 words? Would they really take in each and every one or would they scan through, trying to pick out key pieces of informa- tion? In short, there are lots of good reasons to keep your body text concise. Use bold - <bold> or <strong> - and italics - <em> or <i> - to pick out keywords on the page, but sparingly. This helps both search engines and human readers to identify your key text. But don’t use the underline <u> tag anywhere on your page - it confuses users expecting to find a link! I further recommend that body text is divided into neat paragraphs of no more than three or four sentences - using the paragraph tags <p></p> - and that your phrases that pay are positioned near the start of each paragraph where possible. Obviously, I recommend that you sprinkle your two-, three-, and four-word keyword chains throughout the text, with reasonable frequency. Opinions differ on ideal keyword density. Much depends on how competitive your key words are and how many you are targeting seriously. For your top four (and site-wide) keywords, I would aim for a density of 20% for each individually in sector one on the homepage (where sector one is defined as title + headings + bold text + italicized text + alt text). The general density for regular page text content (sector two) should be 2-4% for your page-specific (and most important) two-word keyphrases, 0.8-1.5% for your three-word chains, and 0.2-0.5% for related keywords (but plenty of them).
The number of words per page is a bit subjective really. If people are looking for a detailed explanation then 400-600 words is not enough, if people are looking for a brief outline 400-60 words may be too much. I don't believe this should be used as a rule or even as a guideline as the number of words is completely dependent on user needs.
Thanks for your point as you said it is subjective if you are optimizing for users and not search engines.. Thanks anyway