The Basics Behind How Search Engines Work

Understanding how search engines work is actually very simple. There's common technology that all search engines share. The main difference between one search engine and another is how it displays its search results.

Search Engine 101
A search engine is a Web site that responds to queries you type with search results that match the information you're looking to find. Type "cars" and you'll get auto-buying Web sites and pages dedicated to the Disney Pixar movie.

How do search engines know these pages exist? It happens in two ways. First, people who own Web sites submit their URLs to search engines for indexing. This tells the search engine's indexing program, known as a spider or bot, to read the information on those pages and add it to the search engine's growing index of pages. This is known as indexing. Spiders start on a home page and then visit every link in a Web site, capturing information about the pages' titles, images, content and links.

Spiders and bots may also find Web sites during their travels around the Internet. If a Web site that's indexed links to your Web site, the spider will continue on to your page and index the contents of your site. It's possible to prevent search engines from doing this by adding a "nofollow" command to off-site links. If you're looking to build traffic to your site, make sure that anyone who links to you doesn't use the "nofollow" code, or the link will be worthless.

Organizing Results
Once pages are indexed, the search engine then decides the order to display them in, which is known as a search engine ranking. High rankings are very valuable, because they increase the amount of visitors that a search engine sends to your site. Each search engine has its own method of determining rankings, and no one outside of a search engine's development team knows the exact rules, but there are some things that help Web pages rise to the top of the rankings.

• Site age. The longer a Web site has been around, the higher it is likely to rank, if it meets other ranking criteria.
• Site content: The content on a site's individual Web pages, as well as the site's overall goal, play a big role in determining rankings. Informational sites, such as Wikipedia or CNN.com, always rank higher than personal sites because they have a tremendous amount of information. E-commerce sites tend to rank below informational sites, though they can earn higher rankings if they have a lot of content or if you use terms like "shop" or "buy" in your search queries.
• Search engine optimization: Sites that target particular keywords or keyphrases and use them in domain names, links, titles and page content will often rank higher for those keywords than sites that don't use them.
• Inbound links: Sites that have a lot of links, particularly links from highly ranked Web pages, move up in search engine results. Different types of links carry different weight. A link from CNN is very valuable, a link from someone's blog may not be.
• Popularity: Search engines strive to deliver the pages that users want as quickly as possible. The pages that get clicked on the most always wind up at the top of search engine results. Those pages won't stay there, however, if the search engine decides that they're spam, which is why Web page owners should never try to trick a search engine into giving a page a top spot. Webmasters who do this risk having their domains banned from search engine results, which means no more traffic going to their sites.