text: Markup languages Another common use of node trees is in web development. In programming, XML is used to communicate information between computer programmers and computers alike. For this reason XML is used to create common communication protocols used in office productivity software, and serves as the base for the development of modern web markup languages like XHTML. Though similar in how it is approached by a programmer, HTML and CSS is typically the language used to develop website text and design. While XML, HTML and XHTML provide the language and expression, the DOM serves as a translator.
  Node type
  Different types of nodes in a tree are represented by specific interfaces. In other words, the node type is defined by how it communicates with other nodes. Each node has a node type property, which specifies the type of node, such as sibling or leaf.
  For example, if the node type property is the constant properties for a node, this property specifies the type of the node. So if a node type property is the constant node ELEMENT_NODE, one can know that this node object is an object Element. This object uses the Element interface to define all the methods and properties of that particular node.
  Different W3C World Wide Web Consortium node types and descriptions:
  Document represents the entire document (the root-node of the DOM tree)
  DocumentFragment represents a "lightweight" Document object, which can hold a portion of a document
  DocumentType provides an interface to the entities defined for the document
  ProcessingInstruction represents a processing instruction
  EntityReference represents an entity reference
  Element 	represents an element