HTML is the language in which Web pages are written. HTML uses tags like <p> and </p> to identify how text is to be structured and formatted within a document.
XHTML is a redevelopment and extension of HTML that makes HTML compatible with XML. XHTML specifies a family of markup languages that are based on HTML but take advantage of the simplicity, extensibility, and powerful toolset of XML.
CSS is a style sheet language that enables Web page writers to specify presentation, sizing, and positioning properties of HTML and XML documents. CSS is used to describe the appearance of a document in a manner that is independent of its content. There are currently two versions of CSS (referred to as CSS1 and CSS2). CSS2 extends CSS1.
The DOM is a model that describes the objects that are available within HTML and XML documents. It describes these objects in a programming language-independent manner as a system of interfaces. It defines the properties of these objects and methods for accessing these objects. The objects can be accessed via programming languages, such as JavaScript and Java.
JavaScript is a programming language for scripting Web pages that was developed by Netscape. It has been standardized by the ECMA and is referred to as ECMAScript. JavaScript has evolved into a general- purpose scripting language - it is no longer limited to Web pages. Microsoft has also developed a version of JavaScript that is named JScript.
DHTML is a combination of HTML, CSS, and JavaScript that enables Web page content to exhibit dynamic behavior. This is accomplished by dynamically changing the properties of document objects in response to user actions and other events.