It’s worthwhile to read The Anatomy of a Large-Scale Hypertextual Web Search Engine, the college thesis paper written by Sergey Brin and Lawrence Page, the founders of Google. Anyone who’s ever been mystified by SEO can learn a lot from Brin and Page’s treatise on the inner workings of their search engine.
You can read the thesis paper here:
http://infolab.stanford.edu/~backrub/google.html