User agent is the name of the browser/spider that is currently visiting a page. For example, “Googlebot/2.1

Usability is how user friendly a web site is. The ease of use that a user can perform an action or task through the user interface

URL rewrite is a technique used to help make web site URLs more user and search engine friendly.

Used interchangeably with web address. Acronym stands for Uniform Resource Locator. URLs can specify the location of a web page, an email address, or a file on an FTP server, among other things.

The term “universe” in the world of advertising means the total population of the target audience.

Unique visitor is a web traffic measuring term which means the registering of at least one hit on one page of a web site from a unique IP address during a specified report period (typically anywhere from twenty-four hours to a month). A subsequent hit(s) by the same IP address is not counted as a [...]

Unethical search engine optimization techniques that are considered unscrupulous and can result in getting sites banned from the search engines. Examples of this include Keyword stuffing, where the site consists of a long list of keywords. Hidden text is when the text on the page is the same color as the background and often consists [...]

Target Audience
The target audience is the market in which advertisers wish to sell their product or service to. Target markets are defined in terms of demographics, psychographics, purchase behavior, media or product usage.
Taxonomy
Taxonomy is a classification system of controlled vocabulary used to organize topical subjects, usually hierarchical in nature.
Text Ad
A text ad is a concise, [...]

Passes trust scores from well trusted sources through to other sites throughout the web.

Google AdWords Traffic Estimator is a tool that provides search volume, average cost-per-click, and position estimates for search advertising in Google’s search results and content network. It can be used to predict advertising performance before starting a campaign.
The Traffic Estimator tool is available free at:
https://adwords.google.com/select/TrafficEstimatorSandbox