Internet és a Web Történelme,
Bevezetés
Kecskeméti Gábor
A/1 336-os szoba – fizika tanszék
Konzultációs idő: Csütörtök 9-11
Előadás: XX. Előadó, Csütörtök 14-16
Gyakorlat: 207-es terem, Csütörtök 12-14
Ütemterv – vázlat
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1. Hálózati alapfogalmak, a web történelme
2. FTP protokoll
3. HTTP protokoll
4. HTML alapozó
5. HTML űrlapok
6. Formázás CSS segítségével
7. ZH
8. DOM modell
9. Javascript
10. HTML 5
11. CGI
12. PHP
13. Ajax
Szeptember 29.-én
mind az előadás
mind a gyakorlat
elmarad!
Pótlást később
beszéljük meg.
Számonkérés - vázlat
• 1 ZH
– Az előadás idejében 7. alkalommal
– Pótlása az utolsó előadás idejében
• 1 Gyakorlati feladat
– Kiadása: 5. hét
– Beszedése: 10. hét
– Pótálására félév közben van lehetőség
• Vizsga: írásbeli + szóbeli
What is the Internet?





The internet is a publicly available, global network of computers
It interconnects billions of Users. For example:
– Businesses
– Citizens
– Governments
– Academic Institutions
– Research Centers
– Libraries
– Etc.
Provides a Common Communications System for Diverse Computing and
Network Environments
Still Rapidly Expanding
Involves Numerous Technologies (Not a Single Technology)
4
Internet History Milestones
1969
ARPANET
R&D Project
1985
NSFNET founded by
1983
DOD Mandated Adoption ofThe National Science
Foundation
TCP/IP
ARPANET
1974
1983
Vinton Cerf
ARPANET Split into
and Robert Kahn Initiated ARPANET and MILNET
TCP/IP
1993
Web Browser “Mosaic”
invented by Mark
Andreesen
INTERNET
1991
World Wide Web
Released by
Tim-Berners Lee
5
ARPANET
• Advanced Research Projects Agency
Network
• The precursor to the Internet
• Developed in the late 60’s and early 70’s
by the US Department of Defense as an
experiment in wide-area-networking that
would survive a nuclear war.
The Path of ARPANET
 December 1969
July
1977 
Images from Heart, F., McKenzie, A., McQuillian, J., and Walden, D., ARPANET
Completion Report, Bolt, Beranek and Newman, Burlington, MA, January 4, 1978
A brief history of the Internet
1961-1972: Early packet-switching principles
• 1972:
• 1961: Kleinrock - queueing
– ARPAnet public demonstration
theory shows effectiveness of
packet-switching
– NCP (Network Control Protocol)
first host-host protocol
• 1964: Baran - packet-switching
in military nets
– first e-mail program
• 1967: ARPAnet conceived by
– ARPAnet has 15 nodes
Advanced Research Projects
Agency
• 1969: first ARPAnet node
operational
Internet Hosts
1969
ARPANET was born. 4 nodes
were inter-connected:
UCLA,SRI,UCSB, U. of Utah
Charley Kline from UCLA sent 1st
packet.
First RFC by Steve Crocker.
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Internet Hosts
1970
RFC maintained by Jon Postel
(the RFC-editor).
ARPANET used NCP (Network
Control Protocol), first end-toend protocol
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Internet Hosts
1971
15 nodes were connected.
Ray Tomlinson of BBN invented
email program.
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160
Internet Hosts
1972
@ was chosen by Ray Tomlinson
to separate the userid and
hostname.
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First computer-to-computer
chat program at UCLA.
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Internet Hosts
1973
Ethernet was invented by Bob
Metcalfe's (Harvard PhD Thesis)
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Internet Hosts
1974
TCP (Transmission Control
Protocol) was invented by Vint
Cerf and Bob Kahn.
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Internet Hosts
1975
First mailing list was created by
Steve Walker.
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# of hosts
Internet Hosts
1978
TCP splited into TCP and IP.
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A brief history of the Internet
1980-1990: new protocols, a proliferation of networks
• 1983: deployment of TCP/IP
• 1982: smtp e-mail protocol
defined
• 1983: DNS defined for nameto-IP-address translation
• 1985: FTP protocol defined
• 1988: TCP congestion control
• New national networks:
Csnet, BITnet, NSFnet,
Minitel
• 100,000 hosts connected
to confederation of
networks
Internet Hosts
1982
DoD used TCP/IP to interconnect networks. Thus, the
Internet!!!
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Internet Hosts
1983
NCP → TCP/IP.
ARPANET was split into
ARPANET and MILNET.
BSD included TCP/IP.
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Internet Hosts
1984
DNS (Domain Name System)
was introduced.
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Internet Hosts
1986
NSFNET was created, connecting
5 super-computers.
IETF was formed.
NNTP was created.
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NSFnet
• National Science Foundation Network
• The National Science Foundation followed
on the earlier ARPANET by creating
NSFNet in 1986 as a 56 Kbps backbone
for the Internet.
– A Backbone is a very-high-speed connection
with huge bandwidth
• Commercialization of the nets began in
1992. By 1995, the National Science
Foundation withdrew its sponsorship.
Internet Hosts
1987
> 10,000 hosts.
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Internet Hosts
1988
First Internet Worm released by
Morris.
CERT (Computer Emergency
Response Team) was formed as
a result.
IRC was created.
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Internet Hosts
1989
> 100,000 hosts
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A brief history of the Internet
1990, 2000’s: commercialization, the Web, new apps
• Early 1990’s: ARPAnet
decommissioned
• 1991: NSF lifts restrictions on
commercial use of NSFnet
(decommissioned, 1995)
• Early 1990s: Web
– hypertext [Bush 1945, Nelson
1960’s]
– HTML, HTTP: Berners-Lee
– 1994: Mosaic, later Netscape
– late 1990’s: commercialization of
the Web
• Late 1990’s – 2000’s:
– more killer apps: instant
messaging, P2P file sharing
– network security to forefront
– est. 50 million host, 100 million+
users
– backbone links running at Gbps
Internet Hosts
1990
ARPANET ceased.
AOL, CompuServe provided dialup service.
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Internet Hosts
1991
WWW was created by
Tim Berners-Lee from CERN.
Linux was released by Linus
Torvalds.
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CERN
• Centre Européen de Recherche Nucléaire
(European Center of Nuclear Research)
• Announced World Wide Web in Aug 1991,
invented by English scientist Tim BernersLee in 1989
• Developed a system to share documents
in a multi-platform environment.
• Three major developments came from this:
– Hyper Text Transfer Protocols
– Hyper Text Markup Language
– Web Browsers
Internet Hosts
1992
> 1,000,000 hosts.
MBONE was created.
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Internet Hosts
1993
Network Solution, Inc was
chosen to provide domain name
registration.
www.whitehouse.gov online.
Mosaic was created.
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Internet Hosts
1994
NSFNET was transformed to
commercial network.
Shopping mall.
Can order pizza online.
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NSFnet in Action
Byte traffic into the ANS/NFSNET T3 backbone from its
client networks for the month of December 1994, the last
heavy usage month prior to the NSFNET’s
decommissioning in April 1995. Backbone service has now
transitioned to a number of commercial centers.
Internet Hosts
1995
NSFNET was reverted back to
research-only network.
Realaudio started.
Netscape IPO.
Win95 released.
Bob Metcalfe predicted the
Internet would collapse.
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Internet Hosts
1996
Browser war (Netscape vs. IE)
began.
tv.com sold to CNET for $15,000.
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Internet Hosts
1998
2M domain names registered.
Compaq bought altavista.com
for $3.3M.
Google founded.
Jon Postel (RFC-editor) died.
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Internet Hosts
2000
Millennium bug.
Dotcom → dotgone.
Clinton made first webcast.
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2001
Wikipedia launched.
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2003
Facebook launched.
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Internet Hosts
2006
> 439M hosts.
10 new computers joined the
Internet every second.
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Internet Map
http://en.wikipedia.org/wiki/Image:Internet_map_1024.jpg
How the Internet works
42
PACKETS
Underlying principle of the Internet: Packet
Switching
• The internet was first conceived in 1969 as ARPANET (Advanced Research
Projects Agency Network) which was used to connect computers in
geographically dispersed research centers
• ARPANET was the first major implementation of a packet switched network
• Previously, data communications were based on circuit switching as in
traditional telephone networks, where a dedicated link is set up for the
duration of the call
• The invention of packet switching in the early 1960’s enabled the
transmission of data over links that are not established beforehand. In packet
switching, data is assembled into packets which are then independently
routed (using routers) to their destination through various links over the
network. This leads to the distribution of resources, an increase in resource
utilization, and increased fault tolerance since a packet may take alternative
routes to reach its destination
• The destination node receives these packets and re-assembles them to
construct the original message
44
• This breakthrough was what made internet a reality
Destination
Source
One possible route for a data packet
Source: http://howstuffworks.com
45
Packets
• Pieces of data divided up for transit
• Packets contain information about the computer
that sent the data and where the data is going.
• If a packet runs into a problem in transit,
it can attempt to find another route.
When all the packets
arrive at their destination,
the recipient computer
reassembles them.
photo copyright Star Trek
Internet Communications
• Data to be transferred is broken up into packets
• Packets are addressed with IP address for
delivery
• Packets travel over the Internet backbone
• Routers give directions along the way, choosing
paths at intersections
• When packets arrive at the destination IP
address, they are delivered through the firewall
to specific ports
ADDRESSING
Addressing Schemes
We know that packets are sent over the network, but how does a packet reach its
destination?
• Three addressing schemes are used concurrently in sending information across the
Internet
– Organizationally-Unique Identifier (OUI)
• This is the 48-bit (MAC) unique address stamped on Network Interface
Cards
– IP Address
• All devices connected to the internet are identified by a unique 32-bit IP
address
• It is via IP addresses that computers in the internet can identify each other
– Domain Name System (DNS)
• Hierarchical, alphanumeric addressing scheme that is a “synonym” of an IP
address
49
IP Address
• Internet Protocol (IP) address
• A unique number assigned to every
computer connected to the Internet
(current version is IPv4)
• Four sets of numbers separated by
periods, called dot-decimal notation
• Each number in the sequence ranges from
0 to 255
Example: 53.160.248.99
• Running out of numbers
The IP Address

Unique 32-bit (4 byte) logical address
– 129.174.1.8 (This one belongs to GMU)
 Made up of two parts
Decimal IP address
– Network Number
• Identifies a network
• Must be assigned by the Internet Network
Information Center (InterNIC)
– Host Number
• Identifies a host on a network
• Assigned by the local network administrator
51
IP Address Classes



There are 5 different classes of IP addresses: A, B, C, D and E.
A, B, and C are available for commercial use
For example, a Class A network could support 126 networks,
each with 16,777,216 hosts
52
IPv4 to IPv6





The number of IP addresses provided by a 32-bit code (IPv4) is
insufficient for the Internet’s current growth trajectory
How many different addresses does a 32-bit number provide?
– 232 = 4,294,967,296
How can we be running short?
– Rapid global diffusion
– Rapid proliferation of wireless devices that require an IP address
– Voice over IP will only increase the shortage
Is there a solution?
– IPv6 is going to increase the address space to 128 bits
– How many addresses will that provide?
Short term work-arounds like Network Address Translation have helped
stall the need to migrate to IPv6, and many predict the transition will be
a rough one.
53
IPv6
• Internet Protocol Version 6
• Designed to replace 20-year-old IPv4
(current IP address standard)
• Number sequence has 8 places of hex
with colons instead of the standard 4
places of decimal with dots
• Will allow more computers to connect to
the Internet
Example: 3ffe:ffff:101::230:6eff:fe04:d9ff
Assigning IP Addresses
• Static – address assigned permanently to
that computer
• Dynamic – new address assigned to that
computer each time it connects to the
Internet
• DHCP – Dynamic Host Configuration
Protocol, software that assigns IP address
to the computer when it connects
Ports
• Each IP address is subdivided into ports,
each port assigned to a single program
• You can browse the Internet using one
port while receiving e-mail using another
port, with a single IP address
NAMING
Internet Address Names
• IP addresses for a particular computer or
web server can change
• Names are assigned to identify Internet
locations, called Domain Names
Example: www.google.com
The Domain Name System

We would go crazy if we would have to remember the IP
addresses of all the web sites that we wanted to visit

The Domain Name System translates between domain names
and IP addresses of devices connected to the Internet
– A domain name (a part of the URL) is a unique alphanumeric
name such as gmu.edu
– The top level domain name is edu and the secondary level
domain name is gmu in the above example (there could be
up to 127 levels, but more than 4 is rare)
59
DNS
• Domain Name Server
• Used to map domain names to IP addresses
and vice versa.
Example:
www.website.com = 255.255.222.22
Top Level Domains
•
•
•
•
•
•
.com – commercial
.net – on the Internet
.org – non-profit organizations
.gov – government agencies
.edu – educational organizations
.mil – military locations
Example: top level domain for
www.google.com is com
Regional Domains
•
•
•
•
•
•
.uk
.jp
.de
.ru
.kr
.br
•
•
•
•
•
•
.it
.fr
.ca
.ar
.es
.pl
Regional domain is a top level domain.
Example: www.british-library.uk
Subdomains
• Any domain to the left of the top level
domain name
• Example: www.weather.com has top level
of com, subdomain of weather
• Example: www.weber.k12.ut.us has top
level of us, which has a subdomain of ut,
which has a subdomain of k12, which has
a subdomain of weber
How DNS works
• When you type a URL into the address portion of your browser,
the browsers’ first task is to convert the domain name into an IP
address so that it can send a request to the appropriate web
server at that IP address for the web page that you are requesting
• To accomplish this task, the browser interacts with a name server,
a machine that maintains lists to translate the domain names into
IP addresses
• Once the browser receives the IP address from the name server, it
sends a request for the web page that you are requesting
• Let us retrieve the IP address of the name server that we are
using…
64
DNS
IP ADDRESSES
Every device connected
has a unique 32-bit
address
Machine Readable
e.g. 151.196.19.22
DOMAIN NAMES
DNS
Translation Between
domain Names and IP
Addresses
Human
Readable
cnn.com
Every device
connected has an
alphanumeric
address
p IP address and domain name allocation requires central administration to
avoid duplication
p Previously administered by U.S. government contract (NSI)
p In 1998, technical coordination assigned to ICANN (Internet Corporation for
Assigned Names and Numbers).
65
ICANN
• Internet Corporation for Assigned Names
and Numbers
• Provides domain name registration
services
• “Cyber Squatting” – the practice of buying
names and selling them back to
companies who wanted to use them, or
buying names very similar to well-known
names to profit from visitors looking for
that well-known name.
Virtual Domain
• A single IP address shared between multiple
domains
• Multiple Web sites at one IP address
• Multiple domain names that access the same
server
Example:
www.wikipedia.com
www.wikipedia.org
www.wikipedia.net
all go to
the same
IP address
URL
• Uniform Resource Locator
• The address of a site on the Internet
• The name of an Internet site (Domain
name)
Example: http://www.irs.gov
The Universal Resource Locator (URL)
Each page of information on the web has a unique address called the
URL at which it can be found
http://faculty.uscupstate.edu/atzacheva/lecture1.html
The document
can be obtained
using the
Hypertext
Transfer Protocol
(HTTP)
1
Protocol
Host Name The Name of
Web Server
2
Host Name
Path to the Web
Page
File Name
Denotes that the File
is Written in HTML
HyperText Markup
Language
3
File Name
69
Anatomy of a URL
Example: http://www.irs.gov
• Begins with protocol needed to
transfer the requested file – http or
https for Web
• Next is main location on the Internet;
for the Web, that is “www”
• Next is the Web server location; in the
example above, it’s the server
named “irs.gov”
• If there is a slash and more data, this
specifies the path and file of the data
on the Web server
Example of a URL
• http://www.schools.utah.gov/cte/it.ht
ml
• Protocol: http
• Web server: schools.utah.gov on
World Wide Web
• File named it.html in folder named
cte, located on that Web server
• Top level domain: gov (government)
• Subdomains: schools sub to utah
PROTOCOLS
Internet protocol stack
•
application: supporting network applications
– FTP, SMTP, HTTP
•
transport: process-process data transfer
– TCP, UDP
•
network: routing of datagrams from source to
destination
– IP, routing protocols
•
link: data transfer between neighboring network
elements
– PPP, Ethernet
•
physical: bits “on the wire”
application
transport
network
link
physical
source
message
segment
M
Ht
M
datagram Hn Ht
M
frame Hl Hn Ht
M
Encapsulation
application
transport
network
link
physical
link
physical
switch
destination
M
Ht
M
Hn Ht
Hl Hn Ht
M
M
application
transport
network
link
physical
Hn Ht
Hl Hn Ht
M
M
network
link
physical
Hn Ht
M
router
Protocols
• Sets of rules or standards that let computers
communicate over the Internet
• Type or size or brand of computer doesn’t
interfere with communication if the protocol
is used
Protocols
• Main protocol is TCP/IP -- Transmission
Control Protocol / Internet Protocol
• More specific protocols:
– HTTP (Hypertext Transfer Protocol) allows
transfer of Web pages via a browser.
– HTTPS (Secure HTTP) allows transfer of
Web pages with encryption and
authentication
– FTP (File Transfer Protocol) allows transfer of
files through the Internet
from one computer to another.
SMTP
• Simple Mail Transfer Protocol
• The Internet standard protocol for
transferring electronic mail messages from
one computer to another.
POP
• Post Office Protocol
• A protocol used to retrieve e-mail from an
e-mail server.
• Must have this to get your e-mail
• POP3, a newer version, can be used with
or without SMTP.
E-mail
• Messages, usually text, sent from one
person to another via the Internet.
• E-mail can also be sent automatically to a
large number of addresses.
(including spam)
• E-mail is never anonymous and never
really private.
USES OF THE INTERNET
Telnet
• Protocol for remote computing on the Internet
• Allows a computer to act as a remote terminal
on another machine, anywhere on the Internet
• Many library and information resources are
accessible through telnet
• Transfers in plain text on unsecured channels
• More secure protocol is Secure Shell
or SSH
Newsgroups
• Discussion groups on the Internet (not on
the Web, which is only one area of the
Internet).
• Newsgroups are classified by subject
matter and do not necessarily deal with
journalism or "news."
• Like a message board but not Web based
• Text only
Gopher
• A widely successful method of listing material
available over the Internet
• Invented in 1993 as the Internet started
exploding in size
• Designed to be much easier to use than FTP,
while still using a text-only interface, like a
table of contents
• Gopher is a client-server system
• Although Gopher spread rapidly across the
globe in only a couple of years, it has been
largely supplanted by the Web
Internet Usage Today
• World Wide Web
• File transfer and file sharing
• Communication such as e-mail and VOIP
(Voice-Over-IP)
• Online chat, Instant Messaging
• Online gaming
• Commerce (banking, shopping)
Understanding the Web
Applications of the Internet
• The internet is used for a many of
applications. For example:
– WWW
– Email
– Instant messaging
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The World Wide Web (WWW)



The world wide web is a sophisticated system for universal information
capture and delivery
The world wide web consortium (W3C) definition of the web: "The
World Wide Web is the universe of network-accessible information, an
embodiment of human knowledge"
Provides information access in ways not previously possible
– Hyperlinked (Hypertext)
– Graphical user interface
– Pictorial and non-text information
– Information that changes rapidly
– Immediate access
– Anyone can author a web site
– Multi-user access to the same information (try that with a book)
– Easily searchable information
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WWW
• World Wide Web
• A system of Internet servers that uses HTTP to
transfer HTML documents
• These documents (Web pages) support links to
other documents, as well as graphics, audio,
and video files
• One can jump from one document to another
simply by clicking on hyperlinks
• Not all Internet servers are part
of the World Wide Web
• The functionality of the WWW is based on 3 main standards:
– URL (Universal Resource Locator)
– HTML (Hypertext Markup Language)
– HTTP (Hypertext transfer Protocol)
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HTTP
• Hyper Text Transfer Protocol
• The most important protocol used in the
World Wide Web
• Protocol for moving hypertext files across
the Internet.
• Requires an HTTP client program on one
end and an HTTP server program on the
other end.
HTTP
• The standard Web transfer protocol is HTTP (HyperText Transfer Protocols). It
is used for document exchange between servers and clients (typically
browsers) in the WWW.
• To retrieve a document, the client first sends a request to the web server and
waits for a reply
• An HTTP daemon/service (a program that waits for http requests) on the
server then handles the request and the document is sent to the client (over a
connection established using TCP/IP – Transmission Control Protocol / Internet
Protocol)
• We recall from previous lectures, that a Protocol is “Agreed upon sets of rules
that provide order to a system or situation.” In this case, a set of
rules/standards for communicating on the Internet.
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Web Client/Server Architecture
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HTML
• Hypertext Markup Language
• The coding language used for creating and
designing hypertext documents on the World
Wide Web
• Must be interpreted by software for Web
browsers
Example:
<html>
<h1>My Page</h1>
</html>
HTML
• HTML is a universal, simple language for formatting text. It
also allows embedding of graphics, and linking of
documents via ‘hyperlinks’.
• ‘Hypertext’ documents allow readers to freely move
around the document, following links to subjects of
interest.
• HTML is a language that is used to specify the structure of
documents for retrieval across the Internet using
browsers.
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Hypertext
• The text that makes up Web page files.
• Hypertext can contain hyperlinks, which are
words or phrases in the document that can be
chosen by a reader (clickable text), which
causes another document to be retrieved and
displayed
Example:
Click here to go to next page.
Web Browsers
• Software that interprets and displays
documents using HTML located on the World
Wide Web
• Web browsers provide a graphical interface
that lets users click buttons, icons, and menu
options to view and navigate Web pages
• Microsoft Internet Explorer, Netscape and
Mozilla Firefox are popular Web browsers