OK, I'll spill the beans. ;)
The perfect keyword density (KWD) to use on a website is 3.14159265%
If you have any KWD other than that, your site cannot possibly contain any useful content, and the search engines know it, and will kill your rankings as a result.
Spammers, of course, do not know this, and therefore almost never have this exact KWD - that's why the search engines work so well most of the time.
Sure, there are a few spammers who have figured it out and manage to write random gibberish until they get a KWD of exactly 3.14159265%, but they are rare. The funny thing is that as soon as they type in enough random gibberish, the text becomes clear and visitors love it! Wierd, huh? Nothing like science to get the job done!
Of course, you could go out and make yours exactly equal, as well. But then the spammer would just go out and match it with 3.141592653%, at which point you'd have to beat them and hit 3.1415926535%, and so on.
This is called SEO (Simple Equation Organization) and is much more accurate than trying to figure out some sort of relevance or usefulness. That's all vague touchy-feely stuff. This is real numbers and decimal places, and is therefore much better and more scientific. The web is about data, technology and hard numbers, not being useful to humans - just ask any systems administrator and they will tell you.
Some other scientific facts:
- There are exactly 31,415,926,535 grains of sand in the Google Sandbox - Coincidence? I think not!
- If, at any point in time, 2 sites actually end up with the *exact* same KWD, there is a GoogleDance and another digit is added to the specification - don't worry, there are lots to go. This happens every few months and it's usually Jill Whalens fault for not counting words on her pages properly. We try to tell her, but she just won't listen...
- Your PageRank (PR) is exactly equal to the actual number of incoming links you have divided by 3.1415 - another coincidence? I doubt it! Check for yourself.
- The reason that MSN and Yahoo! show different listings from Google is because they round off differently, that's all.
If you are doing SEO on a competing site to one of mine or my clients and found the above post useful, then keep up the good work!
(uhh...I didn't think I'd have to announce that the above was a joke/spoof, but apparently there really are people who think this is important stuff. Note to them: you might want to learn about a few of the changes that have been made to search engines in the last, oh, decade or so...)