directory, the name suggests the site is stored in the corresponding categories in the directory, so the user information in the query, keyword search option also can be classified directory layer look. As in the keyword search returns results with the search engines, and is based on information associated websites are ranked, but the human factor to be more of them. If the investigation by a hierarchical directory of a directory site Zhao Dong ranking is determined by the title sequence of the letters (there are exceptions).
Currently, search engines and directories index merges with another trend. The full text of the original number of pure search engine now offers a directory search, such as Google to borrow the Open Directory provides directory classification queries. And like those old Yahoo! directory index through the cooperation with Google and other search engines to expand your search. In the default search mode, the number of directory type search engine first returns sites that match their own directory, such as domestic Sohu, Baidu, Netease, etc.; while others default is a web search, such as Yahoo.