The sites with the most text matches rank highest on the list of results. This method often turns up long lists of obscure and inappropriate sites. Some sites manipulate this system, writing one word hundreds of times on a page, invisibly, to get higher play in the search results. So other methods were developed. The sites with the most links pointing to it are most likely to be read, making it more likely to be relevant to the average user.
Human editors scan Web sites, toss out useless ones and categorize others by subject.
This guarantees you won't come across gross errors, such as finding the history of Turkey under Thanksgiving recipes. But the directories don't have the breadth and reach of automated search engines. One way to make a search more accurate is to personalize searches for users. Motwani said a search engine could get to know you and your preferences by analyzing your bookmarks. If that could be done in a secure way, search tools could create a vague profile about you and target searches based on your interests.