What is the World Wide Web?
The World Wide Web (abbreviated in this document as the "Web")
is a collection of electronically linked documents (called pages) that are accessible
from the Internet. The words document and page
both refer to a single file and are synonymous. You navigate between between Web
pages using two types of links:
- hypertext links
work similarly to clicking a topic in an online help system. A hypertext link
is a connection to another page on the Web or within the current Web site.
You can connect to pages of your own creation, or to pages created by someone
else by placing a hypertext link in a Web page.
- Many Web pages are
longer than can be displayed in the current screen. These Web pages frequently
have links to areas in the same page that are located beyond what can be shown
in a single screen. These types of links are referred to as anchor
links. When an anchor link is clicked, the Web browser displays that
part of the document containing the specified anchor.
A Web site is a group of related pages residing on a Web server.
A Web site can be as small and simple as a single page with no links, all the
way to an extensive interlinked site with hundreds of pages. A user typically
visits a Web site via a home page. When viewed from the perspective of a Web
site designer, a home page is the Web page that automatically
loads when readers access your site on the Web. A home page usually has a file
name of index.html for Web servers that use the UNIX operating
system, or index.htm for those Web servers capable of handling
only three characters for the file name extension. Windows typically uses 3-character
file extensions. When viewed from the perspective of a person using the Web,
the term home page refers to the Web page that automatically loads when the
user first starts a browser. A home page typically contains hyperlinks to other
pages within the Web site and hyperlinks to pages on the Web. For example, when
you visit www.microsoft.com, the Web
server displays the home page for the site.
A Web server is a computer running software that stores and
delivers Web documents to a Web browser. It must have a Web server software
package installed and running at all times to respond to the requests for Web
pages made by Web browsers. The Web server accepts requests for documents from
other computers, and then delivers those documents to clients running a Web
browser. The Web browser then formats those documents and displays them to the
user. Different computer vendors develop and sell different Web servers as described
in the following list.
- Internet Information
Server is the Web server used by Microsoft Windows.
- Sun One Web Server
is sold by Sun Microsystems for UNIX computers.
manufactures servers for UNIX and Linux.
- Other vendors, such as
IBM, also sell Web server software.
For a Web site to work, it must be hosted on a Web server. The following list
describes various Web hosting options:
A Web browser
is a software package that formats documents sent by a Web server and displays
them for viewing. Many Web browsers are available, including Netscape's Navigator
and Microsoft's Internet Explorer. Of course, Netscape Navigator's popularity
has declined significantly in recent years. Figure 1 illustrates the relationship
between a Web server and a Web browser.
- An Internet Service
Provider (ISP) maintains the server where you send requests and makes
space available for you to store your Web site. An ISP typically provides
you with access to the Internet too. Earthlink, WorldNet, and AOL are all
- Free Web hosting is provided
by Geocities and others. However, these free hosting sites often display banner
ads or other advertisements when the site is viewed by the user. In addition,
the amount of free Web space granted by these companies is quite limited.
- A company, or the University
for that matter, will likely have their own Web server(s). UNR has several.
System Computing Services provides Web hosting for the University System as
a whole. In addition, COBA maintains its own Web server. You are visiting
the COBA Web server while viewing this page. There are many more Web servers
on campus. In this exercise, you will use the system wide Web server to host
your Web site.
Relationship between a Web server and Web client
Navigating the Web
To visit a Web site, you enter an Internet address in a format called a Uniform
Resource Locator (URL) in the Web browser. The Web browser then downloads
that Web page from the Web server, and formats the page. Every page on the Web
has a unique address, much like the one for your house. The URL uniquely identifies
the exact location of a Web page on the Web. Note that the term Uniform
Resource Indicator (URI) is often used in place of the term URL.
An example of a URL is shown in the following figure. This is the URL for this
Parts of a URL
The following list describes the parts of the preceding URL:
- Type of protocol used to transfer data. A protocol
is the set of rules that describes how information is transferred across the
Internet between clients and servers. The protocol used by the Web to transfer
data is called the Hypertext Transfer Protocol (HTTP). The
Internet, and most Web browsers, support other protocols. The most common
protocols are listed in Table 1.
Table 1: Common
||Opens a file on a mounted disk volume
||Opens a World Wide Web page
||Connects to a server using the File Transfer Protocol
||Connects to a Gopher server
||Connects to a server using Telnet
||Connects to a Usenet newsgroup
||Sends an electronic mail message
||Opens a secure newsgroup connection
||Opens a secure World Wide Web connection
- Domain name. Identifies the computer that is used to store
the Web page. It usually begins with "www" but does not require those characters.
You can think of the domain name as the Internet name of the computer running
the Web server containing the Web page.
- Directory path. This is the location on the Web server
computer's disk where the Web page is stored. Directory paths are hierarchical.
That is, one directory may contain another directory. These directories ultimately
contain Web pages, and other support files.
- Document name. This is the name of the Web page. The Web
page frequently has a suffix of ".html" or ".htm." These suffixes are an abbreviation
for Hypertext Markup Language, which is a the computer language
used to represent Web pages. As mentioned, index.html and
index.htm have special meaning and are used by Web servers
to denote the beginning or default Web page for that directory. Other operating
systems used for Web servers have other default Web page names, such as "default.html"
or "default.asp". Note that UNIX is case sensitive. Thus, the files
named "Index.html" and "index.html" are not the same. Windows file names are
NOT case sensitive.