WHOIS

A type of search where the query of a domain name shows details of the domain, like when it was registered, by whom, and when it expires.

XENU

A program used for link checking.

XML

Extensible Markup Language. A web programming language that allows web authors to define their own, custom tags. Especially useful in the creation of web-based applications

Yahoo

One of the first and popular web directories, Yahoo continues to be one of the most visited sites on the Internet. Yahoo is a distant second in search engine market share behind Google.