Don't get hung up on precise percentages of so-called "keyword density" and exact placement of phrases on your page. Those are both hallmarks of a kind of "paint by numbers" formulaic SEO that used to be popular several years ago.
At the time, it was thought that by "simply" reverse engineering the SE's algorithms, one could reliably produce pages that would always rank well in the SEs. Whether SEO-by-numbers ever really worked is debatable, but the bottom line is that most old-school algo-chasers have come around to the understanding that with something like 200 ranking factors in play at any given time and over 400 algorithm updates being processed per year, trying to keep up with the algos is a losing proposition.
Not to mention, as it turns out, with as many different variables as the SEs measure, the "ideal" percentage of various page elements is different for each individual page. There are no hard-and-fast numbers you can point to that will always work in every situation. What would be severe keyword overkill for one page works just fine for another, and might even be under-use for a third.
It's a much better idea to simply try to create excellent web pages.
What are the search engines trying to do with all these algo-tweaks and ranking criteria and all? They're trying write a formula that can "think" like a real human searcher so they can give the human searchers what they want. And what do human searchers want? Pages that answer their questions; pages that inform or entertain them; high-quality content that's worth the time they spend reading or viewing it.
So bonciutoma had some good advice: write for humans. Give those seachers the kind of things they're looking for.
So first off,
look at your pages. Do you see the word(s) you're concerned about jumping off the page all over the place? If you highlight the word or phrase in question, does the page light up like the proverbial Christmas tree? Or does the level of usage seem appropriate given the topic of the page and the way in which the words have been integrated into the overall page layout and visual design?
The easiest way to test the actual article content for keyword over-use is to read the copy out loud and see if it sounds crappy to your (human) ears. Better yet, read it into a voice recorder of some sort. Let it sit overnight, then listen the next day to the recording you made. If it sounds to
you as though you're repeating the same words over and over and over and over, then it's going to sound the same way to your site visitors. And that's A Bad Thing.
The SE's tolerance for keyword repetition is much, much higher than the average human site visitor. By the time you get to the point where you've stuffed it too much for the SE's to tolerate, you will long ago have driven off every human visitor.
--Torka
Repeating Keywords Too Much? --> ok, I meant tags not keywords
