online social networking : Web sites where people can meet and interact with one another; examples include MySpace and Facebook.

on-page factor : The HTML tags and the visible content on a Web page.

on-page optimization : The changing of the underlying code of a Web page for the purpose of search engine optimization.

open source : A term for a Web site that allows anyone to access and edit its content.

open-source software application : A computer program whose source code is available for free to the public.

organic search results : Web pages that the search engines find on their own using their spiders. These results are not paid for by advertisers.