Probably the most important single investment any website owner can make is search engine optimization, also known as SEO. Every year the strategies that go into effective SEO become a just a little more advanced and a little more specific. Search engines themselves are constantly refined, responding to user queries more accurately, and recognizing more spam sites. And as search engines evolve, website owners everywhere need to review their SEO strategies every year to make sure they are still the best available.

In the’90s, SEO was simple. You added a few meta tags to your website, and made sure your content was peppered with keywords at a high percentage. Just repeating keywords was once enough to draw traffic. This was back in another era when spider technologies were relatively new, and when website visitors were OK with simple matches that approximated the information they were seeking.

In 2009, however, search engines have evolved to make search more accurate. Google is the prime example. Ten years ago Google’s algorithm counted back-links and prioritized. You got more credit for a back-link to a desirable site, and, as the system developed, you were penalized for having back-links to a spam site. Putting keyword anchor text into links would optimize your site for those keywords, even if they did not appear in your content.

There is a lot of value in the old SEO strategy. It’s still very helpful to integrate keyword-rich links to your site. You still need keywords in your content. What is different, however, is that Google and other engines have been working overtime to find ways to discern quality content from pages that are not spam, but not especially useful, either. Websites don’t just go through popularity contests by building back-links; they must also deliver quality, original content that can pass muster with the language filters.

Certain language patters appear in literature, in news reports, and in countless other sources online. Google and other engines have started distilling these word patterns and integrating them into their algorithms to rule out websites that are clearly keyword stuffing. This makes quality content a lot more valuable than it once was. Website owners once could optimize a page by stuffing it with a 7% keyword density. Nowadays, a 3 to 4% keyword density is optimal. More is not better. If keyword density looks unnatural to a search engine, it will reject the page, even if it is not spam.

The top strategy for search engine optimization in 2009 is still to write useful copy with keyword optimization, combined with back-links to high page-rank sites with carefully chosen anchor text. Just avoid getting greedy. Keyword optimization that does not overreach with great user-friendly content will be the way to keep your page rankings high in 2009.

Justin Harrison is a leading Internet Marketing consultant responsible for the Internet Marketing strategies behind some of the biggest online brands including Amazon, BBC, MasterCard and many others.