The web’s markup language has always been HTML. HTML was primarily was designed as a language for semantically designed for scientific documents, although after its design and techniques over the years have enabled it to be described as number of other types of documents. The HTML, is targeted specially at web applications to be used by users on occasional basis or regular basis from different locations and provide the same results even on low CPU.
History of HTML is very interesting, the development of HTML was started in 1990 and from 1990 to 1995 there are many revisions. With the creation of W3C, the first abortive attempt at extending HTML in 1995 was made with HTML 3.0, the in 1997 stable version of HTML 3.2 is released. HTML4 was completed in 1999 and it become the standard of HTML. In 2000, W3C stopped the improvements on HTML and instead started working on XML based equivalent, as also know as XHTML and in 2000 the first version of XHTML 1.0 was released. Then w3C, started on working on XHTML2, which is not compatible with XHTML or HTML.
In the meantime, parts of API for HTML development by browsers were specified and published under DOM Level 1 in 1998 and in 2000 Started working on DOM level 2 and completed in 2003. The working of DOM level 3 started in 2004 but the closing working group the development has also been stopped by the browsers.
From 2004, the evaluation of new things like RSS, ATOMS, Micro formates etc., started and within a short time span Apple, Mozilla and Opera jointly announced their intention to continue to work under one umbrella of WHATWG. The main objective of the HTML5 was stated that technologies need to be backwards compatible and they try to implement three things HTML4, XHTML1 and DOM Level2 in HTML5 only.
Documents are build from elements and these elements form a tree using the DOM. The features of the elements would be common. Each elements meaning is already defined and how to use each element along with user agent requirements are already defined.
HTML5 has introduced the Microformats also can be know as machine-readable annotations to the documents, so that tools can extract the name/value or pair from the document easily. The some of the examples are vCard, hCalender etc.
DOM means the Document Object Model. Every Document Object has one root element and it does not have the root element then it is not the DOM. In HTML the root DOM element is . Each root element can have multiple child nodes but each child node have only one parent node. Normally, in an HTML page you will observe the HTML starts with HTML then you would fine HEAD and then BODY. Thus, each web pages have the DOM root element.
A content attribute is said to change value only if its new value is different from its previous value; setting an attribute to a value it already has does not change it. The term empty, when used of an attribute value, text node, or string, means that the length of the text is zero (i.e. not even containing spaces or control characters).
Nodes can be cloned, as described in the DOM Core specification. For example, the cloneNode() and importNode() methods of the Node interface both clone nodes, as do a number of algorithms in this specification. Certain HTML elements (in particular, input and script) apply additional requirements on how they are cloned.