On-themerefers to content specific to a particular topic
OntologyAn ontology defines the common words and concepts (meanings) used to describe and represent an area of knowledge, and so standardizes the meanings.
Open Directory ProjectA directory project run by thousands of volunteer editors. In principal, this is a very exciting and powerful way to organise the web.
Open SourceSoftware which is distributed with its source code such that developers can modify it as they see fit.
OperaA fast standards based web browser. See also: Opera.com
OptimizationChanges made to a web page to improve the positioning of that page with one or more search engines.
Organic Search ResultsMost major search engines have results that consist of paid ads and unpaid listings.
Outbound LinkA link from one website pointing at another external website. Some webmasters believe in link hoarding, but linking out to useful relevant related…
Outbound linkslinks that direct "off-site" to another website
OvertureThe company which pioneered search marketing by selling targeted searches on a pay per click basis.
Overture Keyword Selector ToolPopular keyword research tool, based largely on Yahoo! search statistics. Heavily skewed toward commercially oriented searches, also combines singular and…