Web Development: Chapter 2

What are the parts of a URL?

- Scheme - Hostname - Path

An HTTP request and an HTTP response are both composed of four parts:

- Status line - Zero or more header fields - Empty line - Optional message body

What are three things the web involves?

- Text files, known as HTML files, containing links to other text files. - A program, known as a browser, for viewing HTML files. - A set of rules, known as the HTTP protocol, for transferring HTML files among computers.

How many total HTTP requests does a browser send for a web page that does not use any other web resources?

1

______________ main DNS servers exist in the world.

13

When did computer networks evolve?

1960's

If a web browser sends 20 HTTP requests to a web server, how many HTTP responses will the web server likely send to the web browser?

20

IPv6 supports about how many IP addresses?

3.4 x 10^38

Which status code is sent when the web server wants to redirect the browser to a different URL?

301 or 302

Which status code is sent when the web server compares the cached ETag with the server's ETag for a requested web resource, and the two ETags are identical?

304

What is the size of an IP address in IPv4?

32 bits

A typical IP address is _________ bits divided into _______ 8-bit groups.

32, 4

Which status code is sent when the web server is denied permission to the requested URL?

403

Which status code is sent when the requested URL does not point to an existing resource on the web server?

404

How many total HTTP requests does a browser send for a web page that contains four web resources: an image, a video, a CSS style sheet, and a JavaScript file?

5

What is the first step when a computer sends a packet using a domain name over the internet?

A DNS server is contacted and the domain name is converted to an IP address.

Uniform Resource Locator (URL)

A URL (Uniform Resource Locator) is the location of a web resource on the web, such as http://www.cdc.gov/alcohol/faqs.htm.

Browser Cache

A browser cache is an area on the computer's disk where web content can be stored by the web browser for quick retrieval later.

Browser Redirect

A browser redirect is when the web server returns a 301 or 302 status code with a Location header indicating the URL the browser should load next.

Web Site

A collection of related web pages are organized into a website and stored on a web server.

What does a computer network do?

A computer network allows computers to communicate information with each other.

Top-Level Domains

A domain name belongs to one of numerous top-level domains (TLD), such as .com, .net, .org, .edu, and .gov.

Domain Name

A domain name is a name for an IP address, such as the name wikipedia.org for the IP address 198.35.26.96; the name is easier to remember and type.

HTTP Request

A message sent from the web browser to the web server. Often the request asks the web server to send back a web resource like an HTML file, image, CSS style sheet, JavaScript file, or video.

HTTP Response

A message sent from the web server back to the web browser in response to an HTTP request. Often the response contains the requested web resource.

Network Sniffer

A network sniffer is software that monitors network traffic and allows users to inspect HTTP requests and responses.

Hypertext Transfer Protocol (HTTP)

A networking protocol that runs over TCP/IP and governs communication between web browsers and web servers.

IPv6

A new version of the Internet Protocol, IPv6, uses 128-bit addresses, capable of representing 2128 addresses.

Transmission Control Protocol/Internet Protocol (TCP/IP)

A protocol suite that governs how packets of data are transferred over the Internet from one machine to another.

Web Browser

A web browser is a program that downloads an HTML document from a web server, displays the document to the user with the appropriate formatting, and allows the user to interact with the document, such as clicking hyperlinks to access other documents.

Web Page

A web page is a document that is viewed in a web browser.

Web Resource

A web resource is any retrievable item, like an HTML file, image, video, CSS style sheet, etc.

Web Server

A web server is a program that serves web pages to web browsers.

Certificate Authority

A website wanting to use HTTPS must acquire a digital certificate issued by a trusted certificate authority, which contains a public key needed to encrypt data between the browser and web server.

Digital Certificate

A website wanting to use HTTPS must acquire a digital certificate issued by a trusted certificate authority, which contains a public key needed to encrypt data between the browser and web server.

Path

All characters to the right of the hostname in the URL.

Request Method

An HTTP request method indicates the desired action to perform on a resource.

Status Code

An HTTP response status code is a three digit number that indicates the status of the requested resource.

IP Address

An IP address (short for Internet Protocol address) is a computer's unique address on the Internet (like a house's unique address in the world), usually represented numerically like 198.51.100.7.

Entity Tag (ETag)

An entity tag (ETag) is an identifier for a specific version of a web resource. Ex: 34905a3e285dd11. When the resource changes, so should the ETag associated with the resource.

Domain Name Resgistrar

Anyone may register an unused domain name with a domain name registrar.

Scheme

Characters at the beginning of a URL followed by a colon ":" or a colon and double slashes "://".

Before a TCP connection is created, the web browser performs a/an ______.

DNS Lookup

Markup

Document markup is special markings in the document that provide additional information about links, formatting, and images.

___________ names are used more often than IP addresses.

Domain

cnn.com is a(n) _____.

Domain name

Anyone can register an unused domain name with a ____________________________.

Domain name registrar

Country Code Top-Level Domain (ccTLD)

Each country is assigned a unique two-letter country code top-level domain (ccTLD) like .uk (United Kingdom), .ru (Russia), and .de (Germany).

File Transfer Protocol (FTP)

FTP (File Transfer Protocol) was an early way for transferring files over the Internet.

True or false: A 404 message indicates that a domain name is not recognized.

False

True or false: Because Chrome is by far the leading browser worldwide, testing a web page only really needs to be done using Chrome.

False

True or false: Color blindness is so rare that web developers do not have to consider the issue when selecting colors for a web page.

False

True or false: If a web server is down (such as powered off), the server may return a page saying to please try again later.

False

True or false: Really small businesses are exempt from web accessibility requirements.

False

True or false: Unlike the blind, people who are deaf do not need special accommodation for websites.

False

True or false: Web developers typically create web pages using new features available exclusively on a particular browser.

False

True or false: Websites have either an IP address or a domain name, but not both.

False

True or false: With the introduction of IPv6, devices on the Internet no longer use IPv4.

False

The internet began as ___________________.

Four networked computers.

Where does the name world wide web come from?

From the interconnections of computers being like the interconnections of a spider's web.

Which request method is used by the browser to get the same response headers that a GET would generate but without the message body?

HEAD

Where can the HTTP header field If-None-Match be found?

HTTP Request

HTTP/1.1

HTTP/1.1 is the HTTP standard used for most of the web's lifetime.

HTTPS

HTTPS is a protocol that encrypts HTTP traffic between a browser and web server so a network sniffer cannot intercept sensitive information in the HTTP traffic like passwords, credit card numbers, financial transactions, etc.

Hypertext Markup Language (HTML)

HyperText markup language (HTML) is the standard markup language for web documents.

Hypertext

Hypertext is text that has links to other text (and today to images, videos, and more).

ICANN

ICANN, the organization that manages TLDs, now allows companies and organizations to create customized TLDs, like .church, .pizza, and .music.

404

If a web server is reached but the specific requested page isn't found, the server returns a 404 status code, which is a code number for page not found.

What HTTP header field is used to make a conditional request using a datetime?

If-Modified-Since

Second-Level Domain

Immediately after a top-level domain comes a second-level domain, such as wikipedia in wikipedia.org.

World Wide Web

In the early 1990s, Tim Berners-Lee was working at a Swiss research institute named CERN and developed a more convenient way for computers to communicate files over the Internet. Berners-Lee named his creation the World Wide Web, or simply "the web".

Which browser lost the most market share between 2010 and 2015?

Internet Explorer

HTTP/2

Many websites are adopting HTTP/2, a new HTTP standard that speeds-up the transfer of information between web browsers and web servers.

Is Internet browsing more likely to be done using desktop computers or mobile devices in 2020?

Mobile Devices

Do web servers always generate ETags for all web resources?

No

Does a 304 response generally contain a message body?

No

Does capitalization matter in domain names?

No

Is www.nasa.gov a valid URL?

No

Which request method is used by the browser to submit web form data to the web server?

POST

By caching web content, browsers can ___________ the amount of network traffic required to display previously visited web pages.

Reduce

Internet

The Internet began as four networked computers in 1969 but is today the largest and most popular computer network, spanning the entire globe.

Hostname

The complete domain name specified in the URL.

A DNS server's primary role is to convert _____.

The domain name to an IP address.

Linkrot

The general name for a once valid link that now return a 404 status code.

IPv4

The original Internet Protocol, known as IPv4, has 32-bit addresses.

Before HTTP communication begins, what does the web browser do?

The web browser extracts the domain name from the URL being accessed and performs a DNS lookup.

DNS Lookup

The web browser performs a DNS lookup by sending the domain name to the local DNS and getting back the IP address of the web server hosting the domain name.

Root Servers

Thirteen main DNS servers (called root servers) exist in the world, and a computer's operating system or an ISP keeps a reference to the root servers' IP addresses.

FTP (File Transfer Protocol) was an early way for ________________________ over the Internet.

Transferring files

True or false: A random website is more likely to have a visitor with low vision than a visitor who is totally blind.

True

True or false: Domain names are hierarchical.

True

True or false: Web developers can sometimes ignore really old web browsers.

True

URL Shortening

URL shortening is a technique to create shorter URLs that redirect to longer URLs.

W3C

W3C (the World Wide Web Consortium) is the international standards organization that controls web standards.

DNS Server

When a computer sends a packet using a domain name over the Internet, the first step is to contact a DNS server to convert the domain name to an IP address.

Is the following a valid URL? http://www.nasa.gov/cubequest/details/#.VOaO_VPF9U9

Yes

Is the following a valid URL? http://www.whitehouse.gov/

Yes

Which scheme should a URL use to provide a secured HTTP connection to a web server?

https

Which file does the following URL access? http://www.weather.com/summer/temperatures.htm

temperatures.htm

What is the hostname of the following URL? http://www.weather.com/summer/temperatures.htm

www.weather.com