SEO
In the Search engine Optimization I learned that certain things can lower your ranking because of search engine spam. Spam includes: unrelated keywords, redirects, Gibberish, etc… These tricks along with many others are easily detected by search engines and have a bad affect or the search engines perception of the site.
I also learned the difference between a search engine and a directory. A search engine utilize crawlers and directories are updated by people. DMOZ provides results for a variety of search engines.