Obfuscation – This technique is similar to that of cloaking.Meta tags or contents of a page are presented in a wrong way. A normal looking page is presented to the user but not submitted to search engines. This causes the page to rank low on search engines.

Off Page Criteria – The data and information that a search engine uses to ranks pages that are not present on the web page.
Example: Link popularity, Linkage etc.

On Page Criteria – The data and information that a search engine uses to ranks pages that are present on the web page.
Example: Title of the page, Content on the page etc.

Open Directory Project (ODP) – A directory initially known as NewHoo, run by human volunteer editors. The ODP is used by many search engines and www.dmoz.org itself.

Opt-In – Email marketing program used by websites that allows users in receiving information from webmasters (owner of websites).

Opt-Out - Email marketing program in which users assumes a permission to send emails to everyone who has not precisely specified that they do not want to receive such emails.

Outbound Link - Link that point from your website to webpages of different domains.

Overture - The Pay Per Click advertising program by Yahoo. In 2005 it is renamed to Yahoo! Search Marketing.