Keyword Density

I'm asked about keyword density and what is the optimal keyword density for a page.

Keyword density doesn't matter as much as the theme. This is where LSI comes into play. Each page should have many variations of the same keyword/kw phrase, so the SE's know what its about. Theming downwards like this gambling>>>online gambling>>>online gambling reviews

This is why I target online gambling reviews as one of the keyword phrases. The link juice will funnel upwards to all related phrases. The key is to mention the primary keyword on each page more frequently than the other related terms, and to link out from this page to the page below it, within the content (text). So If page 1 was targeting gambling I would mention 'online gambling' in the content, but not more frequently than gambling. Then in sticking with the theming principal I would include 'online gambling reviews' on the 'online gambling' page, again, not more frequently than 'online gambling'.

So there is no right or wrong density. I've even read when there is only one instance of a keyword on a page that ranks well for it. The key is the navigational structure, link sculpting and theme of your site.

Can you over-do it? Yes, so don't go crazy. That's called keyword stuffing.