History and versions of html

History and Versions of HTML

                   Tim Berners-lee is the person who defined HTML.In 1990, Tim Berners-Lee was working at CERN(European Organization for nuclear research).

             

             He included the elements that could define title,paragraphs,hyperlink,headings,simple lists,address blocks and so on.

              But in that version of HTML there was no facility for producing tables or fill-in forms and images within a document.

              In 1994 Tim Berners-Lee launched the World Wide Web consortium(w3c)for producing standards for web technologies.W3C is also defined the standards for HTML.

              As an outcome of W3C's efforts HTML 2.0 adopted web standard within it.the W3C released its HTML 4 recommendation in december 1997.the current version HTML 4.01 which is now followed for producing web documents.

             The meta language used to define the syntax for HTML 4.01 is SGML(Standard Genralized Markup Language).

             In 1998, the W3C introduced the Extensible Markup Language(XML)which is a restricted version of SGML.then a new version of HTML came up,which is called XHTML.(eXtensible Hypertext Markup Language).The syntaxes of XHTML are defined using XML,rather than SGML.   

           The XHTML is syntactically identical to HTML.but XHTML  follows certain restrictions.these restrictions are mentioned by following difference. 

Difference between HTML and XHTML

            HTML                                        XHTML

1)HTML is Hypertext Markup      1)XHTML is Extensible
  language.                                         Hypertext Markup Language.

2)An application of SGML            2)An application of XML.

3)Can have empty/open tags         3)All the unclosed tags must be 

    eg:<br>,<p>                                   closed.eg:<br/>,<p>,</p>                                                   

4)No hard rule on structures          4)Structure of the elements 

   of the elements eg:<p><b>             should be followed e.g <p>

   the difference</p></b>                   <b>the difference</b></p>

5)Attributes have quotes as            5)Attributes have quotes       

   optional e.g:                                     mandatory eg:

<font color=#ff0000>                         <font color=#ff0000?>

6)Attributes values not                    6)Attributes values are

   significant. e.g:                                 important.e.g:

<input type="checkbox"checked>      <input type="checkbox"

                                                               checked="checked">

7)Case Sensitive:The tags and        7)Case Sensitive:The tags and

   attributes can be of uppercase           attributes must be of 

   or lowercase as per the                       lowercase

   preference.    

8)All the content can be put             8)All the content has to be put

   under body element                          in blocks(p under body 

                                                             element)

9)HTML is not mandatory               9)XHTML document must 

   for one root element                         have one root element.

    

The relationship between SGML,XML,HTML and XHTML is as given below

-------------    superset of     -------------- 

- SGML   - ----------------->-XML       -

-------------                          --------------

       :                                            :

       :derives                                : Derives

       :                                            :

-------------    superset of      ---------------

-HTML   - ------------------>- XHTML-

-------------                           ---------------

       :                                            :

       :                                            :

       :                                            :

-------------                            ---------------

 | SGML  |                             |    XML       |

 |    tool -  |<--------------------|      tool       |

--------------                            --------------