Obfuscation - A seldom-used term, more often called Spamdexing. It refers to the misrepresentation of Meta Tags and page content in order to gain an advantage in the search engines. The term is sometimes differentiated from Spamdexing in that it is used to refer to pages that, through stealth, rank highly although they are poorly optimized. The idea is to deliberately mislead others who might steal the page.

OBL - Abbreviation for Outbound links.

ODP - Abbreviation for Open Directory Project a web directory, also known as DMOZ. A massive directory continually expanded by volunteers. A listing in ODP results in the page automatically being listed in many other directories and search engines.

Off The Page - The number of factors that impact the ranking of a web page but that are not located on the web page itself. Inbound links, anchor text etc. are examples of off the page factors.

Off-Page Elements - The opposite of on-page elements. Elements that are outside the direct control of the web site developer and are influential in determining search engine ranking. Examples of off-page elements are links pointing to a web site and anchor text in links pointing to web site. However web site developers still have some degree of control over these elements for example directory submissions. Search engines are relying more and more on these elements when determining ranking because they are more resistant to spamming/abuse.

Off-Page Factors - Factors that alter search engine positions that occur externally from other Website. By having many links from other sites pointing to yours is an example of Off-Page Factors.

Offshore Link Building - This process should be known as Financially Prudent Methodology for Increasing Brand Awareness.

One-way Links - Links to a web site that are not reciprocated i.e. no link exists to the web site that is doing the linking. These types of links are powerful in building link popularity. For more information read my link popularity article.

On-page Elements - The opposite of off-page elements. Elements that are within direct control of the web site developer and are influential in determining search engine ranking. Examples of on-page elements are Meta Tags, page text, title tag text, site link structure etc. These elements are prone to keyword spamming and other similar forms of abuse so the search engines do not look to them as much as off-page elements when determining ranking.

On-Page Factors - Factors that determine search engine positions that occur internally within a page of a website. This can include site copy, page titles, and navigational structure of the site.

Ontology - In the context of search engines it refers specifically to a file that defines relationships between words.

OOP - Abbreviation for Over Optimization Penalty. A theory that applies if one targets only 1 keyword or phrase, and the search engines view the linking efforts to be SPAM.

Open Text - A directory listing only business sites.

OpenRank - A suggestion to make a web-wide ranking system as opposed to Google's Pagerank.

Operators - The words "AND", "NOT" and "OR" as used in Boolean Searching.

Optimization - The process of making Web site or Web page search engine friendly. Optimization may involve design, layout changes, new text for the title tags, meta tags, alt attributes, headings, etc.

Optimized Content - A form of content writing, which is optimal for websites due to the amount and placement of relevant keywords and keyword phrases.

Opt-In - When a user willing joins a subscription to a newsletter or some other service.

Opt-in Email - An email that is explicitly requested by the recipient.

Opt-out - The type of program that assumes inclusion unless stated otherwise.

Organic Listings - Listings that are not pay for placement or pay per click and are obtained solely by the engine's algorithm and are based on the merit of the page. Paid inclusion content is also often considered "organic" even though it is paid for.

Organic Search - Organic search is when the search engines find the website through natural processes.

Origination Page - The origination pages are typically new or obscure pages that haven’t yet attracted interest from the larger, more inter-linked web community, or that are only linked to from other origination pages.

Orphan Page - A page that has a link to it, but has no links to any other sites.

OS - Abbreviation for Operating System

OSEO - Abbreviation for Organic Search Engine Optimization.

Outbound Link - A link from subject site to any other site.

OutLinks - Same as Outbound Links

Overture - Yahoo Search Marketing, Yahoo keywords bid program for webmasters.