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Today I will be discussing the various types of search engines that exist today on the Internet. In order not to overwhelm the reader I will divide this article into four parts.
Four major search engine types
1) crawler based search engines.
2) hybrid engines (META engines and engines using other engines' results).
3) directories (edited and maintained by humans).
4) paid inclusion engines and pay-per-performance.
1. Crawler based searchengines
Crawler based searchengines use special software, known as crawler, bot, spider, or robot, to automatically and regularly visit websites to create and supplement their gigantic web page databases.
When a crawler visits your website, your web server will return the HTML source code of your page to the spider and after it reads your pages, it will compress the data and store it in the gigantic database called the search engine index.
The index, sometimes called the catalog, is like a giant book containing a copy of every web page that the spider finds. If a web page changes, then this book is updated with the new information.
The process of compressing and storing webpages is also known as indexing.
After your page has been indexed, it will appear on search engine results pages for the words and phrases most common on the indexed web page.
The reading of your webpages by the crawler is also known as crawling or spidering.
Crawlers ignore graphics and flash animations but read the META tags and give more value to text that is closest to the beginning and end of a webpage, text wrapped in links, headers, image ALT descriptions, and so forth. These graphics are additional ‘obstacles' on it's way to your content and the crawler may rank your page low, no one will find it on the searchengine and no one will be able to appreciate the design of your website.
Later, when someone searches the engine for particular terms, your page will be pulled out of the index and included in the search results.
The searchengine software applies a sophisticated technique(algorithm) to sift through millions of pages recorded in the index to find matches to a search and rank them in order of what it believes is most relevant.
Many factors are taken into consideration and the page is given a position and rank, within other results found for the surfer's query. This process is called ranking.
Basically the crawler based search engine has three parts:
1) the crawler
2) the index
3) search engine software
Sometimes it can take a while for new pages or changes that the spider finds to be added to the index. Thus, a web page may have been spidered but not yet indexed. Until it is indexed it is not available.
SEO (search engine optimization) is the solution for making your page more search-engine friendly. The optimization is mostly oriented towards crawler-based engines, which are the most-popular and common on the Internet. The best is ofcourse to keep both human and crawler visitors happy and combine graphics and search engine optimization.
Google is a typical crawler based searchengine. In my opinion it is better to have quality content then quality graphics.
What would you prefer?: A fast loading, ugly looking, website with quality content text or a slow loading website, filled with nice graphics and pictures that no one is able to find?
Tommorow:
Directories (edited and maintained by humans)
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SEO 
