To find what you're looking for on the Internet, you will use one or all of the following:
Directories - A listing that is divided into named categories and the entries assigned to the categories are partly or entirely edited by humans. You look things up by finding a category you want and seeing what it contains or searching with keywords. This type of search is becoming very popular.
Indexes - Collects all the items, extracts keywords from them and makes a big list of sites. You search it by giving some words that seem likely (key words), and it finds all the entries that contain your search term(s).
Search engines – Specifically programmed search systems find items in their own unique way.
These special tools help you find information on the 'Net'. All the directories and indexes are in the broad category called search engines. The search engine will sort through millions of pages it knows about and present you with ones that match your topic. The matches will even be ranked, so that the most relevant ones come first. So how do search engines go about determining relevancy? They follow a set of rules, with the main rules involving the location and frequency of keywords on a web page. The easier it is for the search engine to pick you out, the better your chance to get noticed. If your search term(s) is(are) not found, or the engine can not match all the terms, it will find pages that match as well as possible. Your accessibility to the outside world is limited by the quality of the site relative to the standard requirements of search engines. Nobody does it exactly the same, which is why the same search on different search engines will produce different results. It is important to focus your design for the most popular search engines.
What factors go into the calculation?
Ranking criteria varies from search engine to search engine. Most calculate page rankings based on these elements:
Prominence of the keyword searched in the viewable text
Frequency of the keyword searched in the viewable text
Site Popularity, i.e. the number of links to your site from other web sites
"Weight" of the keywords
Proximity of keywords
Prominence, frequency, and weight of keywords in the <TITLE> tag(s)
Prominence, frequency, and weight of keywords in the <META NAME="DESCRIPTION">
Prominence, frequency, and weight of keywords in the <META NAME="KEYWORD">
Keywords in <H1> or other headline tags
Keywords in the:
<A HREF="http://yourcompany.com/page.htm"></A> link tags
Keywords in ALT tags
Keywords in <!-- > comment tags
Keywords contained in the <INPUT TYPE="HIDDEN" NAME="HIDDEN" VALUE="include list of keywords here"> the hidden form tag
Keywords contained in the URL or site address, e.g.,
Grammatical correctness and natural-sounding word patterns
Abstain from using formatting, repetition, and word arrangement that could be considered as spam.
Spam is the Internet term for unwanted or false e-mails and submissions. If a word does not pertain, do not put it in.
Search Engine Comparison Information