Taxonomies of Directory

Taxonomies are categorized directories of information. Directory uses a structured way to categorize sites, thats why Directory differs from the index used by a search engine. An often-used analogy is that a directory is like the table of contents in a book. In other words, the directory tells you how the book is organized, while the index allows you to search within the book for specific keywords.

By working with the two most important structured directories: the Open Directory Project (ODP) and the Yahoo! Directory.
It is not so well kept secret that one of the best approaches for getting good placements in the search engine listings is to enter through a back door, by listed in the 2 directory that I've mentioned above.