How Search Engines Use Web Crawlers
It is the search engines that finally bring your website to the notice of the prospective customers. Hence it is better to know how these search engines actually work and how they present information to the customer initiating a search.
Search engines use crawlers or spiders to index websites. When a search engine discovers your website, either through an incoming link or from a submission by you, it will send crawler to catalog all the pages on your site. These crawlers are completely automated. The crawler visits your site, reads the contents, titles, meta tags, links and will also follow links on your site. When it's finished, the crawler will return the information back to a central depository, where the data is indexed for quick access later. The crawler will index any of the sites you link to as well. Some search engines limit the number of pages per site that are indexed, so if you want everything indexed, keep your site small!
The search engine will send the crawler out to check for new or updated pages periodically. When this happens is determined by the rules of each specific search engine.
A spider is like a program that creates a book of your site - where it contains the table of contents, the actual content and the links and references for all the websites it finds during its search, and it may index up to a million pages a day.
Search engines that use crawlers: Google, AltaVista, Lycos and Excite.
When a web surfer asks a search engine to locate information on keywords, the search engine checks it's index and local copies of your site, it doesn't search the web. The reason for different rankings on different sites is because each search engine uses different algorithms to search its own depositories.
Search engines use a lot of different ways to determine how to rank a site, some use frequency and location of keywords, but most of them put a special emphasis on the anchor text of incoming links. By determining what words people use to link to your site, it then figures out what your site is about and which search terms to rank it highly for.
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Published July 15th, 2008
Filed in Marketing