Unique IP Addresses - The number of unique IP addresses that visited the site in question during the given time frame. This is not to be confused with unique users. However, the count of unique IP addresses can serve as a lower bound for the number of unique users. IP addresses normally provide a fairly low count for unique users due to the fact that most mega proxies (AOL, MSN, ect) mask all of their users behind a single IP address and therefore appear as one user.
Unique Users - An unduplicated count of all individually identified machines that made a visit to a selected domain during a given analysis period.
Untraceable Session - A period of visitor interaction with a website for which the visitor cannot necessarily be distinguished as unique or not.
Usability Testing - Usability-testing is the measurement of how well a website aligns with the behaviours of online users, enabling them to complete their tasks efficiently, effectively, and satisfactorily.
User - A person who accesses a website; a user might be responsible for multiple visits to the site over a period of time, or make multiple visits during one session.
User Agent - A user agent is a generic term for any program used for accessing a website. This includes browsers (such as Internet Explorer or Netscape), robots and spiders, and any other software program that acts as an "agent" for a someone or something seeking information from a website.
Username - A Username is name used to gain access to a computer system. Usernames, and usually passwords, are required in multi-user systems. In most such systems, users can choose their own usernames and passwords.
Viral marketing - Spreading a brand message using word of mouth from a few points of dissemination. Typical techniques include using email messages, jokes, web addresses, film clips and games that get forwarded on electronically by recipients.
Visit - A page request or a series of page requests by a visitor to a given domain. If, after the initial page request occurs and 30 minutes elapses without a subsequent page request, the visit session is closed. A new visit session is opened upon the next page request to the given domain.
Visitor - A Visitor is a construct designed to come as close as possible to defining the number of actual, distinct people who visited a website. There is of course no way to know if two people are sharing a computer from the website's perspective, but a good visitor-tracking system can come close to the actual number. The most accurate visitor-tracking systems generally employ cookies to maintain tallies of distinct visitors.
Visitor Session - A Visitor Session is a defined period of interaction between a Visitor (both unique and untrackable visitor types) and a website. The definition of a Session varies depending on the type of visitor tracking employed.
W3C - The W3C, or World Wide Web Consortium, is a standards body dedicated to ensuring interoperability between all the varied system and network types that comprise the World Wide Web part of the Internet. The W3C log format is commonly used by several web server software systems, such as Microsoft IIS. For more information, see the W3C website.
Web Server - This is a vague term whose meaning must be determined by the context in which it's used. It will mean one of two things: The physical computer that acts as a server. This is a computer just like any other. It is called a server because its main function is to deliver web pages. Often there is nothing particularly special about a server's hardware, it's only a server because of the software it runs. The software that serves the web pages (HTML). This special software runs all the time (it is a daemon-- pronounced demon) and listens for requests for web pages. When a request comes in from the web, the server software figures out which site it is for and sends out the requested file, which is usually the home page of the site (e.g., index.htm).
