People in general know nothing about the algorithm that runs the search engines. Many of you don't know what an algorithm is. I really count myself among that group even though I know it has something to do with statistical analysis.

The information about using the search engines to their best advantage (optimization) is really only derived by the author's personal experience and an effort to predict what the "robots" will do next. No one has access to behind the scenes knowledge.

The formula that calculates who is listed at the top of the search results keeps changing. As people find new ways to "cheat" to improve their website ranking, methods of calculating relevance also change. What made your website #1 yesterday might not be a factor today.

The internet is constantly growing. Therefore, that means the number of matching search results goes up. This factor in itself is enough to cause you to lose rank for specific keywords.