A Uniform User Interface
The third fundamental idea in the World Wide Web is that it should be simple to use. What dos simple mean? First, during the exploration of the hyperspace, what the users see on their screens, what they have to do to activate a link, or make a search should be as natural as possible, and vary as little as possible from one client system to another. Second, the users should as far as possible be unaware of incompatibilities in data representation between the local system and the remote servers. They should also not care how the information is brought to the local system. This is what is called is called the uniform user interface concept in the Word Wide Web.
The WWW protocol specifies a format for writing WWW-compliant documents. Why another new format? We explained that the specification of modern documents must separate layout and logical structure. In addition, the logical structure of a hypertext document must allow for the specification of anchors and links. This is what the WWW document format, called Hyper Text Markup Language(HTML), does: it defines simple element structures and the specification of hyperlinks. HTML is simply one document type(DTD) of the Standard Generalized Markup Language(SGML).
The HTML format therefore lets us build client programs, the browsers, which will hide the way in which the final documents-those attached to links and pointed at by URLs-are actually described.