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. There are basically two types of search engines. The first is by robots called crawlers or spiders. Search Engines use spiders to index websites. When you submit your website their required submission page, the search engine spider will index your entire site. A ‘spider’ is an automated program that is run by the search engine system. Spider visits a web site, read the content on the actual site, the site's Meta tags and also follow the links that the site connects. The spider then returns all that information back to a central depository, where the data is indexed. It will visit each link you have on your website and index those sites as well. Some spiders will only index a certain number of pages on your site, so don’t create a site with 500 pages! The spider will periodically return to the sites to check for any information that has changed. The frequency with which this happens is determined by the moderators of the search engine. A spider is almost like a book 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. Example: Excite, Lycos, AltaVista and Google. When you ask a search engine to locate information, it is actually searching through the index which it has created and not actually searching the Web. Different search engines produce different rankings because not every search engine uses the same algorithm to search through the indices. One of the things that a search engine algorithm scans for is the frequency and location of keywords on a web page, but it can also detect artificial keyword stuffing or spamdexing. Then the algorithms analyze the way that pages link to other pages in the Web. By checking how pages link to each other, an engine can both determine what a page is about, if the keywords of the linked pages are similar to the keywords on the original page. Most of the top-ranked search engines are crawler based search engines while some may be based on human compiled directories. The people behind the search engines want the same thing every webmaster wants - traffic to their site. Since their content is mainly links to other sites, the thing for them to do is to make their search engine bring up the most relevant sites to the search query, and to display the best of these results first. In order to accomplish this, they use a complex set of rules called algorithms. When a search query is submitted at a search engine, sites are determined to be relevant or not relevant to the search query according to these algorithms, and then ranked in the order it calculates from these algorithms to be the best matches first. Search engines keep their algorithms secret and change them often in order to prevent webmasters from manipulating their databases and dominating search results. They also want to provide new sites at the top of the search results on a regular basis rather than always having the same old sites show up month after month. An important difference to realize is that search engines and directories are not the same. Search engines use a spider to "crawl" the web and the web sites they find, as well as submitted sites. As they crawl the web, they gather the information that is used by their algorithms in order to rank your site. source: top10optimizer.com
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