Each search engine uses a different method to determine which sites to list first when you do a search--that's why the results vary so greatly. In general, these are some of the factors that are taken into account:

if your search term is in the URL

When you search for a particular keyword, like travel, most search engines will look for that keyword in a site's URL. However, even if a site is at www.travel.com, that doesn't mean it will automatically be first on the list. Variations in search algorithms can make seemingly unrelated links float to the top and obvious links disappear. For example, we searched for cnet using Magellan and AltaVista, and none of our pages were among the first 100 listed. However, our pages were listed in WebCrawler when we did the same search, while Magellan returned lots of non-CNET sites that had cnet elsewhere in their URL).

if your search term is in the title

Another factor considered is the title of the page. This is the phrase that appears at the top of your browser, above the navigational buttons. In HTML, the title is defined using the <title></title> tag. In other words, whatever words are placed between <title> and </title> in an HTML document will be indexed by most search sites. Theoretically, if a site has the word movie in its title, it's more likely to be listed when you do a search for movie sites.

how often--and where--your search term appears in the text

Some search engines--like AltaVista, Infoseek, or Excite--send out spiders that actually retrieve the full text of the pages they visit. So when you do a search for a word, such as Hawaii, they look through the pages in their database and return a list of the ones that include the word Hawaii. One factor that determines how high a particular page appears on the list of results is how many times the word you searched for appears. So a document that mentions Hawaii seven times will probably be listed ahead of a page that mentions Hawaii once. If you search for a phrase, like New York, documents that include the two words close together should appear higher on the results list than a document that includes the word new and then the word york five sentences later.

if your search term is in the site's description

Search engines use different methods to generate the site descriptions that appear in the list of results when you do a search. Some engines just use the first 200 words of the document--which is why you sometimes come across incomprehensible descriptions. Others, such as Excite and Lycos, use proprietary technology to generate their summaries. Still others, like Infoseek and AltaVista, support an HTML tag known as the META description tag. This tag allows Webmasters to write their own site description. It's included in the HTML document and is read by robots or spiders, but it's not visible on the site itself unless one views the site's source code. Besides using these site descriptions in their list of results, search engines will look in the description tag for keywords when you conduct a search. Engines that don't support the META description tag will look for keywords in whatever description they do use.

Example--if Billy Bob wanted his own description of his car repair site to appear in search engine listings, he'd use the META description tag, like so:

<META name=description
content=Internationally renowned auto mechanic Billy Bob answers all your questions. Unquestionably the best car repair site on the entire World Wide Web.>

if your search term is in the keyword tag

Another HTML tag that influences how a site is indexed by search engines is the META keyword tag. Like the description tag, this tag allows Webmasters to influence how their site will be ranked by search engines, but without having to show visitors any extra text. For example, a site for a business that does Web marketing can include a keyword tag that defines keywords such as marketing, promotion, or advertising. These words form part of the code for a Web page, but they aren't visible to people who visit the site. (It's kind of like including washing instructions or fabric content on a tag inside a shirt, rather than printing it on the outside.) However, not all Webmasters use keyword tags, and not all search engines look for them.

Example--Billy Bob has decided to use the META keyword tag to influence how his car repair site is ranked:

<META name=keywords
content=car repair car repair car repair car repair auto mechanic auto mechanic auto mechanic auto mechanic car repair car repair>

Keep in mind that these factors weigh more or less heavily depending on the search engine you're using, and search engines are constantly changing and updating their formulas to determine their relevancy ratings. The catch? Savvy Webmasters can use several tricks to manipulate their page rankings. Read on to find out how.