The most exhaustive result is obtained by using several search engines , since the indexing criteria of these information factories vary and none of them covers the whole web on its own. Good worldwide indexes include Yahoo and WWW Virtual Library . Haku.net and Fennica focus on Finnish web material. Indexes use varying classifications and material selection criteria . Also the frequency of update varies.
Some indexes are simple lists, others make use of database solutions .
If you search for information using index services it means that you are mainly browsing through links. It is important to first find the right index and then proceed to the right subcategories. As is typical of hypertext, when information and different types of media are linked also many search services become linked. There is no end in sight for this development. They are virtual discussion circles specialized in different subject areas allowing you to take part in conversation, distribute information, and ask for advice.