How Search Engines Work

As search engine optimisation relies on developing a website to achieve a high ranking with the major search engines, it is important to develop some knowledge of how the search engines actually work. Not all search engines are the same however and understanding the differences between them can help with any proposed optimisation.

The Different Types of Search Engines
The average web surfer is likely to be very familiar with undertaking searches on the Internet. While the sites or tools used to undertake a search are generally referred to as "search engines", there are in fact three different types of search-related sites, as follows:

• Search Engines – examples include Google, AltaVista, Teoma, MSN, & Inktomi
• Directories – examples include Yahoo, LookSmart, & Open Directory (DMOZ)
• Portals – examples include AOL, HotBot, Lycos & Excite

How They Work
There are important differences between the types of search-related sites. Search engines maintain massive databases of websites that users can search for using any type of keywords or phrases. These databases are compiled by computer programs known as "spiders" or "robots" which effectively "crawl" the entire web and index each site that it finds. The way that individual search engines index and sort their results can vary significantly though as they all use different criteria and in different combinations.

Directories do not rely on crawling the web but instead have real people review and index submitted sites. Directories therefore rely on completely different criteria in assessing the relevancy of various sites.

Portals generally present search results from other search engines or directories. Achieving a high ranking with a portal will therefore rely on gaining a high position with the source search engine or directory.

Rankings and Relevance
While the various search engines use different criteria and apply different weightings, there are two main factors that are applied, namely:

• Content – including frequency of search terms, location of search terms on a page, design of the site, and number of pages containing search terms.
• External factors – including popularity of the site, links pointing to the site, and alliances with similar businesses.

© Copyright 2003-2008 Ausnetech Pty Ltd   A.B.N. 35 104 843 450