XHTML – is short for eXtensible HyperText Markup Language. XHTML is a hybrid between XML and HTML and designed for network devices as a method of displaying web pages on network and portable devices. XHTML was first released January 26, 2000.
XML – is short for eXtensible Markup Language. XML is a specification developed by W3C starting with the recommendation on February 10, 1998. XML is similar to HTML, XML uses tags to markup a document, allowing the browser to interpret the tags and display them on a page. Unlike HTML, XML language is unlimited (extensible) which allows self-defining tags and can describe the content instead of only displaying a page’s content.
XMPP – it stands for Extensible Messaging and Presence Protocol, is a communications protocol for messaging systems. It is based on XML, storing and transmitting data in that format. It is used for sending and receiving instant messages, maintaining buddy lists, and broadcasting the status of one’s online presence. XMPP is an open protocol standard. Anyone can operate their own XMPP service, and use it to interact with any other XMPP service. The standard is maintained by XSF, the XMPP Standards Foundation.
XSS – a security exploit that takes advantage of security design flaws in web generated pages. If the dynamic pages from a legitimate site do not have very robust rules, users machines can be exploited by a 3rd party to present false links or dialog boxes that appear to be from the legitimate site but are not. A specific instance of an XSS vulnerability is known as an XSS hole.