If I type in "graphic design" into the yahoo search engine, how does it choose the order in which links appear

Answer 1

Each engine uses a different proprietary algorithm that is a closely guard commercial secret. How Web Search Engines Work http://www.webopedia.com/DidYouKnow/Internet/2003/HowWebSearchEnginesWork.asp

There are well over 200 hundred factors in the algorithms and it is possible with experience to guess at some of the most important of these. The building of your site with this in mind is called search engine optimization http://www.seo-blog.com/tutorial.php