In 1980, physicist Tim Berners-Lee, who was an independent contractor at CERN , proposed and prototyped ENQUIRE, a system for CERN researchers to use and share documents.
In 1989, Berners-Lee and CERN data systems engineer Robert Cailliau each submitted separate proposals for an Internet-based hypertext system providing similar functionality. The following year, they collaborated on a joint proposal, the WorldWideWeb ( W3 ) project,which was accepted by CERN.

The first publicly available description of HTML was a document called HTML Tags, first mentioned on the Internet by Berners-Lee in late 1991.It describes 22 elements comprising the initial, relatively simple design of HTML. Thirteen of these elements still exist in HTML 4.

The purpose of a web browsers  (like Internet Explorer) is to read HTML documents and display them as web pages. The browser does not display the HTML tags, but uses the tags to interpret the content of the page.

The Extensible Hypertext Markup Language, or XHTML, is a markup language that has the same depth of expression as HTML, but also conforms to XML syntax.

While HTML prior to HTML5 was defined as an application of Standard Generalized Markup Language (SGML), a very flexible markup language, XHTML is an application of XML, a more restrictive subset of SGML. Because they need to be well-formed, true XHTML documents allow for automated processing to be performed using standard XML tools—unlike HTML, which requires a relatively complex, lenient, and generally custom parser. XHTML can be thought of as the intersection of HTML and XML in many respects, since it is a reformulation of HTML in XML. XHTML 1.0 became a World Wide Web Consortium ( W3C ) Recommendation on January 26, 2000. XHTML 1.1 became a W3C Recommendation on May 31, 2001.

In the late 1990s, many considered that the future of HTML lay in the creation of a version adhering to the syntax rules of XML. The then current version of HTML, HTML 4, was ostensibly an application of Standard Generalized Markup Language (SGML); however the specification for SGML was complex, and neither web browsers nor the HTML 4 Recommendation were fully conformant with it. By shifting the underlying base from SGML to the simpler XML, HTML would become compatible with common XML tools. Servers and proxies would be able to transform content, as necessary, for constrained devices such as mobile phones.

Another key advantage was extensibility. By utilising namespaces, XHTML documents could include fragments from other XML-based languages such as Scalable Vector Graphics and MathML. Finally, the renewed work would provide an opportunity to divide HTML into reusable components (XHTML Modularization) and clean up untidy parts of the language

An XHTML document that conforms to an XHTML specification is said to be valid. Validity assures consistency in document code, which in turn eases processing, but does not necessarily ensure consistent rendering by browsers. A document can be checked for validity with the W3C Markup Validation Service. In practice, many web development programs provide code validation based on the W3C standards.

The Extensible Markup Language (XML) is a general-purpose specification for creating custom markup languages  It is classified as an extensible language, because it allows the user to define the mark-up elements.
XML's purpose is to aid information systems in sharing structured data, especially via the Internet, to encode documents, and to serialize data.

XML began as a simplified subset of the Standard Generalized Markup Language (SGML), meant to be readable by people via semantic constraints; application languages can be implemented in XML. These include XHTML , RSS, MathML, GraphML, Scalable Vector Graphics, MusicXML, and others. Moreover, XML is sometimes used as the specification language for such application languages.

XML is recommended by the World Wide Web Consortium  It is a fee-free open standard. The recommendation specifies lexical grammar and parsing requirements.

The versatility of SGML for dynamic information display was understood by early digital media publishers in the late 1980s prior to the rise of the Internet. the mid-1990s some practitioners of SGML had gained experience with the then-new World Wide Web , and believed that SGML offered solutions to some of the problems the Web was likely to face as it grew. Dan Connolly added SGML to the list of W3C's activities when he joined the staff in 1995; work began in mid-1996 when Sun Microsystems engineer Jon Bosak developed a charter and recruited collaborators. Bosak was well connected in the small community of people who had experience both in SGML and the Web.

XML was compiled by a working group of eleven members,supported by an (approximately) 150-member Interest Group. Technical debate took place on the Interest Group mailing list and issues were resolved by consensus or, when that failed, majority vote of the Working Group. A record of design decisions and their rationales was compiled by Michael Sperberg-McQueen on December 4, 1997.

The XML Working Group never met face-to-face; the design was accomplished using a combination of email and weekly teleconferences. The major design decisions were reached in twenty weeks of intense work between July and November 1996, when the first Working Draft of an XML specification was published. Further design work continued through 1997, and XML 1.0 became a W3C Recommendation on February 10, 1998.

XML 1.0 achieved the Working Group's goals of Internet usability, general-purpose usability, SGML compatibility, facilitation of easy development of processing software, minimization of optional features, legibility, formality, conciseness, and ease of authoring. Like its antecedent SGML, XML allows for some redundant syntactic constructs and includes repetition of element identifiers. In these respects, terseness was not considered essential in its structure.

An XML document has two correctness levels:

Cascading Style Sheets (CSS) is a stylesheet language used to describe the presentation of a document written in a markup languages  Its most common application is to style web pages written in HTML and XHTML, but the language can be applied to any kind of XML document

CSS can be used locally by the readers of web pages to define colors, fonts, layout, and other aspects of document presentation. It is designed primarily to enable the separation of document content (written in HTML or a similar markup language) from document presentation (written in CSS). This separation can improve content accessibility, provide more flexibility and control in the specification of presentation characteristics, and reduce complexity and repetition in the structural content (such as by allowing for tableless web design). CSS can also allow the same markup page to be presented in different styles for different rendering methods, such as on-screen, in print, by voice (when read out by a speech-based browser or screen reader) and on Braille-based, tactile devices. CSS specifies a priority scheme to determine which style rules apply if more than one rule matches against a particular element. In this so-called cascade, priorities or weights are calculated and assigned to rules, so that the results are predictable.

Styles Solve a Common Problem

As the two major browsers - Netscape and Internet Explorer - continued to add new HTML tags and attributes (like the <font> tag and the color attribute) to the original HTML specification, it became more and more difficult to create Web sites where the content of HTML documents was clearly separated from the document's presentation layout.

To solve this problem, the World Wide Web Consortium( W3C ) - the non profit, standard setting consortium, responsible for standardizing HTML - created STYLES in addition to HTML 4.0.

Style Sheets Can Save a Lot of Work

CSS is a breakthrough in Web design because it allows developers to control the style and layout of multiple Web pages all at once. As a Web developer you can define a style for each HTML element and apply it to as many Web pages as you want. To make a global change, simply change the style, and all elements in the Web are updated automatically.

Style sheets have existed in one form or another since the beginnings of SGML in the 1970s. Cascading Style Sheets were developed as a means for creating a consistent approach to providing style information for web documents.

As HTML grew, it came to encompass a wider variety of stylistic capabilities to meet the demands of web developers. This evolution gave the designer more control over site appearance but at the cost of HTML becoming more complex to write and maintain. Variations in web browser implementations made consistent site appearance difficult, and users had less control over how web content was displayed

To improve the capabilities of web presentation, nine different style sheet languages were proposed to the W3C's www-style mailing list. Of the nine proposals, two were chosen as the foundation for what became CSS: Cascading HTML Style Sheets (CHSS) and Stream-based Style Sheet Proposal (SSP). First, Håkon Wium Lie (now the CTO of Opera Software) proposed Cascading HTML Style Sheets (CHSS) in October 1994, a language which has some resemblance to today's CSS. Bert Bos was working on a browser called Argo which used its own style sheet language, Stream-based Style Sheet Proposal (SSP). Lie and Bos worked together to develop the CSS standard (the 'H' was removed from the name because these style sheets could be applied to other markup languages besides HTML).

The CSS Working Group began tackling issues that had not been addressed with CSS level 1, resulting in the creation of CSS level 2 on November 4, 1997. It was published as a W3C Recommendation on May 12, 1998. CSS level 3, which was started in 1998, is still under development as of 2008.

In 2005 the CSS Working Groups decided to enforce the requirements for standards more strictly. This meant that already published standards like CSS 2.1, CSS 3 Selectors and CSS 3 Text were pulled back from Candidate Recommendation to Working Draft level.

The World Wide Web (commonly abbreviated as "the Web") is a system of interlinked hypertext documents accessed via the Internet. With a Web browser, one can view Web pages that may contain text, images, videos, and other multimedia and navigate between them using hyperlinks. Using concepts from earlier hypertext systems, the World Wide Web was begun in 1989 by English scientist Tim Berners-Lee, working at the European Organization for Nuclear Research (CERN) in Geneva, Switzerland.

In 1990, he proposed building a "web of nodes" storing "hypertext pages" viewed by "browsers" on a network, and released that web in 1992. Connected by the existing Internet, other websites were created, around the world, adding international standards for domain names & the HTML language. Since then, Berners-Lee has played an active role in guiding the development of Web standards (such as the markup languages in which Web pages are composed), and in recent years has advocated his vision of a Semantic Web

The World Wide Web enabled the spread of information over the Internet through an easy-to-use and flexible format. It thus played an important role in popularising use of the Internet, to the extent that the World Wide Web has become a synonym for Internet, with the two being conflated in popular use.

Viewing a Web page on the World Wide Web normally begins either by typing the URL of the page into a Web browser, or by following a hyperlink to that page or resource. The Web browser then initiates a series of communication messages, behind the scenes, in order to fetch and display it.

First, the server-name portion of the URL is resolved into an IP address  using the global, distributed Internet database known as the domain name system, or DNS. This IP address is necessary to contact and send data packets to the Web Server.

The browser then requests the resource by sending an HTTP request to the Web server at that particular address. In the case of a typical Web page, the HTML text of the page is requested first and parsed immediately by the Web browser, which will then make additional requests for images and any other files that form a part of the page. Statistics measuring a website's popularity are usually based on the number of 'page views' or associated server 'hits', or file requests, which take place.

Having received the required files from the Web server  , the browser then renders the page onto the screen as specified by its HTML, CSS, and other Web languages. Any images and other resources are incorporated to produce the on-screen Web page that the user sees.

Most Web pages will themselves contain hyperlinks to other related pages and perhaps to downloads, source documents, definitions and other Web resources. Such a collection of useful, related resources, interconnected via hypertext links, is what was dubbed a "web" of information. Making it available on the Internet created what Tim Berners-Lee first called the WorldWideWeb in November 1990. Berners-Lee has said that the most important feature of the World Wide Web is Error 404, which tells the user that a file does not exist. Without this feature, he said, the web would have ground to a halt long ago.

The Internet Protocol Suite (commonly known as TCP/IP) is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. Today's IP networking represents a synthesis of several developments that began to evolve in the 1960s and 1970s, namely the Internet and LANs , which emerged in the mid- to late-1980s, together with the invention of the World Wide Web by Tim Berners-Lee in 1989 (and which exploded with the availability of the first popular web browser: Mosaic ).

The Internet Protocol Suite, like many protocol suites, may be viewed as a set of layers. Each layer solves a set of problems involving the transmission of data, and provides a well-defined service to the upper layer protocols based on using services from some lower layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that can eventually be physically transmitted.

Inside TCP/IP

IP Address

Domain Name

• TCP - Transmission Control Protocol
  TCP is used for transmission of data from an application to the network. TCP is responsible for breaking data down into IP packets before they are sent, and for assembling the packets when they arrive.
  
  
• IP - Internet Protocol
  IP takes care of the communication with other computers. IP is responsible for the sending and receiving data packets over the Internet.
  
  
• HTTP - Hyper Text Transfer Protocol
  HTTP takes care of the communication between a web server and a web browser. HTTP is used for sending requests from a web client (a browser) to a web server, returning web content (web pages) from the server back to the client.
  
  
• HTTPS - Secure HTTP
  HTTPS takes care of secure communication between a web server and a web browser. HTTPS typically handles credit card transactions and other sensitive data.
  
  
• SSL - Secure Sockets Layer
  The SSL protocol is used for encryption of data for secure data transmission.
  
  
• SMTP - Simple Mail Transfer Protocol
  Used for transmission of e-mails.
  
  
• MIME - Multi-purpose Internet Mail Extensions
  The MIME protocol lets SMTP transmit multimedia files including voice, audio, and binary data across TCP/IP networks.
  
  
• IMAP - Internet Message Access Protocol
  Used for storing and retrieving e-mails.
  
  
• POP - Post Office Protocol
  Used for downloading e-mails from an e-mail server to a personal computer.
  
  
• FTP - File Transfer Protocol
  FTP takes care of transmission of files between computers.
  
  
• NTP - Network Time Protocol
  Used to synchronize the time (the clock) between computers.
  
  
• DHCP - Dynamic Host Configuration Protocol
  Used for allocation of dynamic IP addresses to computers in a network.
  
  
• SNMP - Simple Network Management Protocol
  Used for administration of computer networks.
  
  
• LDAP - Lightweight Directory Access Protocol
  Used for collecting information about users and e-mail addresses from the internet.
  
  
• ICMP - Internet Control Message Protocol
  ICMP takes care of error-handling in the network.
  
  
• ARP - Address Resolution Protocol
  Used by IP to find the hardware address of a computer network card based on the IP address.
  
  
• RARP - Reverse Address Resolution Protocol
  Used by IP to find the IP address based on the hardware address of a computer network card.
  
  
• BOOTP - Boot Protocol
  Used for booting (starting) computers from the network.
  
  
• PPTP - Point to Point Tunneling Protocol
  Used for setting up a connection (tunnel) between private networks.
  
  

ActiveX is a component object model (COM) developed by Microsoft for Windows. By using the COM runtime, developers can create software components that perform a particular function or a set of functions. A software application can then compose one or more components in order to provide the functionality it intends to. Many Microsoft Windows applications including many of those from Microsoft such as Internet Explorer, Microsoft Office, Microsoft Visual Studio, Windows Media Player, etc. use ActiveX controls to build their feature set as well as encapsulate their functionality as ActiveX controls so that the functionality can be embedded in other applications. Internet Explorer also allows the ActiveX controls to be embedded inside web pages

ActiveX controls are small program building blocks that can be used to create distributed applications that work over the Internet through web browsers. Examples include customized applications for gathering data, viewing certain kinds of files, and displaying animation.

ActiveX controls can be compared in some sense to a Java applet, since both are designed to be downloaded and executed from web browsers. However, there are a few differences. Java applets can run on nearly any platform, while ActiveX components are only compatible with Microsoft's Internet Explorer web browser and the Microsoft Windows operating system. ActiveX controls are also granted a much higher level of control over Windows than Java applets, making them both more powerful and dangerous. Malware , such as computer viruses  and spyware , is often distributed as ActiveX controls in webpages.

ActiveX controls can be written in MFC, ATL, C++, C#, Borland Delphi and Visual Basic. Common examples of ActiveX controls are the command button, list box, dialog boxes, and even the Internet Explorer browser.

Dynamic HTML, or DHTML, is a collection of technologies used together to create interactive and animated web sites by using a combination of a static markup language (such as HTML), a client-side scripting language (such as JavaScript), a presentation definition language (such as CSS), and the Document Object Model DOM.

DHTML allows scripting languages to change variables in a web page's definition language, which in turn affects the look and function of otherwise "static" HTML page content, after the page has been fully loaded and during the viewing process. Thus the dynamic characteristic of DHTML is the way it functions while a page is viewed, not in its ability to generate a unique page with each page load.

Web pages authored using hypertext markup language (HTML) may contain multilingual text represented with the Unicode universal character set.

The relationship between Unicode and HTML tends to be a difficult topic for many computer professionals, document authors, and web users alike. The accurate representation of text in web pages from different natural languages and writing systems is complicated by the details of character encoding, markup language syntax, font, and varying levels of support by web browsers.

Web pages are typically HTML or XHTML documents. Both types of documents consist, at a fundamental level, of characters, which are graphemes and grapheme-like units, independent of how they manifest in computer storage systems and networks.

An HTML document is a sequence of Unicode characters. More specifically, HTML 4.0 documents are required to consist of characters in the HTML document character set: a character repertoire wherein each character is assigned a unique, non-negative integer code point. This set is defined in the HTML 4.0 DTD , which also establishes the syntax (allowable sequences of characters) that can produce a valid HTML document. The HTML document character set for HTML 4.0 consists of most, but not all, of the characters jointly defined by Unicode and ISO/IEC 10646: the Universal Character Set ( UCS ).

Like HTML documents, an XHTML document is a sequence of Unicode characters. However, an XHTML document is an XML document, which, while not having an explicit "document character" layer of abstraction, nevertheless relies upon a similar definition of permissible characters that cover most, but not all, of the Unicode/UCS character definitions. The sets used by HTML and XHTML/XML are slightly different, but these differences have little effect on the average document author.

UTF-8

UTF-8 encodes each character (code point) in one to four octets (8-bit bytes), with the 1-byte encoding used for the 128 US-ASCII characters. The Internet Engineering Task Force (IETF) requires all Internet protocols to identify the encoding used for character data, and the supported character encodings must include UTF-8.The Internet Mail Consortium (IMC) recommends that all email programs be able to display and create mail using UTF-8
more about UTF-8 : http://en.wikipedia.org/wiki/UTF-8

UTF-16

Windows-1252

ANSI

ASCII

EBCDIC

UCS

PHP is a scripting language  originally designed for producing dynamic web pages. It has evolved to include a command line interface capability and can be used in standalone graphical applications.

While PHP was originally created by Rasmus Lerdorf in 1995, the main implementation of PHP is now produced by The PHP Group and serves as the de facto standard for PHP as there is no formal specification. PHP is free software released under the PHP License, however it is incompatible with the GNU GPL , due to restrictions on the usage of the term PHP.

PHP is a widely-used general-purpose scripting language that is especially suited for web development and can be embedded into HTML. It generally runs on a web server, taking PHP code as its input and creating web pages as output. It can be deployed on most web servers and on almost every operating system and platform free of charge. PHP is installed on more than 20 million websites and 1 million web servers