Introduction

The World-Wide Web (WWW, W3) is a tremendous network of information servers scattered across the globe, and instantly accessible to any well-connected computer user. It is a very sophisticated and elegant source of hypermedia documents containing information on everything from esoteric academia to official Congressional literature to current weather conditions and just about anything else along the way.

The Web offers not only access to an impressive magnitude and depth of information, but also a standardized hypermedia format, which makes navigation of the Web quick, intuitive and consistent, regardless of computer platform. This interactive interface places the Web far beyond other wide-area servers. All the catch phrases frequently used to describe the up-and-coming "Information Superhighway" find justification now in this vast, multimedia, open-access network.

Surfing the Web?

For example, when one wishes to surf Cyberspace, the preferred waters are those servers on the Web. It offers support for more data formats and greater access to Internet services than any other information retrieval system. The Web browser, or if you like, surfboard, of choice is called Mosaic. Available to Macintosh, Windows, and X Windows users, this popular software interface allows users to access every format of information available on the Web. Offering a full palette of multimedia viewers and converters, Mosaic is the intended front-end to the Web.

Other information services can handle only text files with proficiency. Documents in formats such as GIF, JPEG, or SND can be retrieved via FTP, but must be separately handled by other applications to be converted and displayed. With Mosaic, users can obtain not only public domain text files, but also sound files, graphics, and digital movies, all in popular, standardized formats. Beyond this, Mosaic offers a consistent mouse-driven interface when accessing remote computers, even when implementing secondary protocols. But one of the most exciting features of Mosaic is its ability to support hypertext and hyperlinks.

Some Basic Terminology

Despite its conspicuous name, hypertext differs from regular text in only one regard: hypertext incorporates links to other documents. For example, a hypertext document may include references to a glossary, so that whenever the reader encounters a new term, that word contains a hyperlink to its definition in the glossary. The reader may click on the word and the computer will seamlessly retrieve its glossary entry. Many popular software packages are now implementing hypertext in their on-line help.

Hypermedia is the natural extension of hypertext to all of the other media supported by the Web. In one instance, a user may click on a small thumbnail sketch of a graphic and then receive a full-sized copy of the graphic file which the thumbnail references. For example, when first beginning to use Mosaic, you may encounter a small picture of Vice President Al Gore. Naturally, you'll want the full image to store locally, print out and tack above your desk. Mosaic makes the process as simple as a point and click. Hyperlinks to sound files and digital movies are also commonly found on the Web.

More than Just a Web

Another exciting feature of the Web is its seamless links to other kinds of information servers. Popular information systems on the Internet include Gopher, WAIS, anonymous FTP, Usenet, Archie, Veronica, and Telnet. Web users can access all of these servers as easily as they can retrieve hypermedia documents. Of course, these packages do not utilize the hyperlinks or HTML which characterize the Web, but the vast resources which already exist, for example, on Gopher servers, makes access to these sites vitally important for any Web user.

Also, when accessing these sites, Mosaic maintains an interface which is similar to the standards intended for each kind of server. That is, when a Web user following a hyperlink to a Gopher server, the user is presented with the familiar menu scheme common to all Gopher servers. At the same time, users enjoy the advantage of Mosaic's mouse-driven interface, which most Gopher servers do not usually offer.

This ability to access the existing universe of information servers, to provide a system fluent in all of the most popular protocols, was one of the main focuses of the Web project. In addition, Web servers utilize a new protocol and file format.

Understanding HTML and HTTP

The Web operates on the popular client-server model. That is, a Web server is a computer solely devoted to serving documents which are requested by clients. The client computer receives the document, which contains formatting information, interprets this information, and renders the document on screen for the user. This model of operation reduces the amount of work performed by the server in order to maximize efficiency and accommodate several clients simultaneously.

The language which servers and clients use to communicate is called HyperText Transmission Protocol (HTTP). Web servers are also referred to as HTTP servers. The language in which Web documents are written is called HyperText Markup Language (HTML). This language is written in standard ASCII and contains formatting codes which indicate to the client computer how to present text to the user and where the actual hyperlinks are located. The ability to represent text in bold, italics, or underlined, and in various paragraph structures is another advantage that Mosaic and the Web offer above other information servers such as Gopher and WAIS.

On screen, a hyperlink may appear as simply an underlined word. That is, as the user reads through a document, any word which contains a reference to another document, or to another part of the same document, will be emphasized, most commonly by underscoring. These words are called anchors. The user sees the anchor, but the hyperlink itself is invisible to the user, though it is contained in the HTML document. The link itself consists of a Uniform Resource Locator (URL), which is usually a pointer to a certain file contained on a remote HTTP (or Gopher, FTP, News, Telnet, etc.) server. Virtually any file or service on the Internet can be absolutely represented by a URL. A typical URL might look like this:

Again, since the URLs are, for the most part, invisible or unnecessary to the user, it is not necessary to memorize or even look at these addresses.

Just What is Available on the Web?

Navigating the Web is something of an art form in itself. It may take some time to feel comfortable chasing links all across the globe from your desktop, but there can be no better advice than to jump on and hang on. Each version of Mosaic has characteristics unique to its platform, but they all share the same basic interface. It is absolutely user-friendly, and greets you eagerly with tips and examples on how to begin exploring the Web. Mosaic also features a Hotlist, where you can record links to you favorite servers and documents, and the ability to personally annotate documents with text or audio entries.

The Web includes a vast amount of information, from many different categories. Perhaps the biggest sources of information come from universities, colleges, and research centers around the world. Current research, results, programs of study, papers and exhibits represent a few of the types of information available from these servers. Government agencies, such as NASA, also have Web servers, and provide text and graphical information regarding their current projects. In addition, there is a large body of currently debated legislation proposals and historical documents on-line from government sites. Private companies, especially those closely linked to information and communication technology, also offer Web servers. These servers may contain official press releases, product descriptions or product support information.

Anyone who uses the Web will be impressed with their own abilities to find obscure and interesting data, as well as the more practical and public information. Here are some examples of documents retrievable from the Web:

Everyone who starts browsing through the Web quickly acquires their own personal list of favorite sites. Here are a few to try yourself:

Some Background on the Web

The World-Wide Web was first proposed in March 1989 at the European Laboratory for Particle Physics (CERN). The Web was originally proposed by Tim Berners-Lee to permit a more efficient system of information sharing and dissemination to support groups located around the world.

The vision of the Web was to create a program which could understand all the preexisting information server protocols, as well as the most popular file formats, and provide a consistent interface to all of them. That is, the Web would provide seamless access to all of these different information sites, retrieve information in just about any standard format, and display, animate or play it for the user. In essence, it was a program to remove the barriers of information transfer caused by incompatible computer platforms, communication protocols and data formats. Beyond this, the Web would introduce a new protocol (HTTP) and file format (HTML) which would support a rapidly growing body of hypermedia information.

Interest in the Web spread outside the community of high energy physics, and gained support from various groups around the globe. In February 1993, the National Center for Supercomputing Applications (NCSA) at the University of Illinois released alpha versions of Mosaic for X Windows, with full support for X Windows, Macintosh and Microsoft Windows platforms following in September. This program added the hypermedia capabilities lacking in the previous Web browsers, and fulfilled the vision of the program.

Currently, the Web is the most sophisticated, and arguably the most elegant, information system available on the Internet. The Web has steadily grown since its implementation, and will continue to accelerate in growth.

How to Obtain More Information

To begin exploring the Web with Mosaic, connect via ftp to

and log in anonymously. Get the file "README.FIRST" to receive full instructions on transferring and installing Mosaic on your machine. For more information on Mosaic, take a look at their own home pages for Macintosh, X Windows, or Windows. NCSA requests that, after obtaining a copy of Mosaic, you immediately change you home page to something local, as the number of HTTP requests at their default page has reached astronomical proportions.

If you have Internet access only through a line terminal, you can still surf the Web with one of the following "line-mode" browsers:

These programs support a wide range of "dumb" terminals, and although they lack the capabilities of interpreting and displaying the sophisticated formatting and multimedia available to Mosaic users, they will open up the Web to just about anyone. Welcome to the Web and happy surfing!

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This document is maintained by Andrew_Flint@hmc.edu.
Last updated September 20, 1994.