The best way to think of the relationship between on-page factors and off-page factors is this: on-page factors are like tuning up a car for a race to make sure all the parts run reliably and strongly, off-page factors are the fuel.

So, if your car isn't running right, all the fuel in the world isn't going to make it go. Similarly, if you don't have any fuel, even the most highly-tuned car will go nowhere. In the world of search optimization, you need both.

Google, more than any other search engine, is a great innovator with respect to measuring inbound linking power and then adjusting search results in favor of sites that enjoy high number of inbound links. The reasoning is sound; sites with a higher number of inbound links are most likely to be superior to those that have a lower number of inbound links. This innovation that links between websites by "votes" for the quality of the destination site, is now employed by all major search engines. And, for the most part, the principle does ensure superior search results when users search for information through a search engine.

What Google wants, ideally, is for inbound links to be natural links, not artificially generated links. If a website owner earns inbound links through paid link-building schemes, then the methodology is skewed—the low-value site that has paid for inbound links now enjoys higher ranking power as a superior site with fewer links. That result is not what is intended by the inbound link component of the search algorithms.

The search engines know that in the real world, not all linking between websites will be natural. They are fully aware that webmasters attempt to game the system through a variety of linking practices that range from relatively innocent reciprocal linking to more sinister practices like automated forum spamming and hidden links. Google forbids "link schemes" in its webmaster guidelines, and penalties are common.

The task for the legitimate webmaster is to secure links naturally. Natural linking will ensure that your site will never suffer a penalty, and links that you obtain naturally will carry much more power than links obtained through any schemes or artificial means. We cover specific link building methods in Chapter 6, Building Links.

Over-optimization occurs when a website's elements are present in too high a proportion or too high in power for a given keyword phrase. Over-optimization yields poor search performance. An example of over-optimization would be the incessant use of keywords on your website so that your keywords represent 50 percent of the total density of words on the page. Another example would be a website with 100 inbound links, all with the same exact anchor text. First-time SEO hobbyists tend to be ensnared by over-optimization as they zealously pursue the new elements of SEO that they learn; they stuff keywords into title tags, meta tags, body text, and secure links all with the same anchor text.

Over-optimization is difficult to quantify, and can be difficult to detect and repair. The best way to think about over-optimization is that websites should never be "too perfect." Remember, a search engine ultimately must employ mathematics to its ranking criteria. It's easy for a search engine to mathematically determine that a page with a keyword density—keywords as a percentage of total words on the page—exceeding 8 percent is attempting to game the algorithm and therefore should not be ranked.

Thinking about over-optimization in this way, repetition is often the main culprit. To avoid over-optimization, you'll need to be vigilant to watch for excessive repetition of terms in the main elements of a website and in inbound links.