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Transcript 
What is the Internet?
Session 4: World Wide Web
Elena Silenok @silenok
Charlie Robbins @nodejitsu
Questions? Just Raise Your Hand
Topics
• History, evolution
• Architecture
• Browsers (overview, differences)
• Acronyms (HTML, CSS, AJAX)
• Security
History
• 1970s/1980s - local networks, email, IM,
chat, file sharing, MUDs, forums
MUD
WWW != Internet
• One of 65,535 possible services on the
Internet (email, ftp, telnet, IM, etc.)
• Developed as a way of posting formatted
documents online at CERN
• 1993 - Marc Andreessen adds pictures to
web display
Sir Tim Berners-Lee
Concept (1989)
August 6, 1991
• First web browser/editor
• First web server (NeXT computer)
• First web pages - described the project
itself (alt.hypertext newsgroup)
• URL, URI, HTML, HTTP
Mosaic (1993)
Netscape (1994)
1990s
• Netscape IPO - 1995
• Internet Explorer - 1995
• Browser wars - Netscape free in 1998,
acquired by AOL
• Antitrust - DoJ vs Microsoft in 1998
• AOL sues Microsoft, gets $750 million, IE
royalty-free for 7 years (2003)
How It Works
• User types URL (www.google.com)
• IP address lookup in DNS (74.125.226.180)
• HTTP GET request to 74.125.226.180
• HTTP response + content
• Web browser parses the HTML
HTTP response/request
GET /index.html HTTP/1.1
Host: www.example.com
HTTP/1.1 200 OK
Date: Mon, 23 May 2005 22:38:34 GMT
Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT
Etag: "3f80f-1b6-3e1cb03b"
Accept-Ranges: bytes
Content-Length: 438
Connection: close
Content-Type: text/html; charset=UTF-8
HTML
• HyperText Markup Language
• Tags - <img>, <a href>, <div>, <em>, <script>
• Structure and interpretation of a hypertext doc
<html>
<head>
<title>My web page about World Wide Web</title>
</head>
<body>
<p>The <b>World Wide Web</b>, abbreviated as <b>WWW</b> and ...</p>
</body>
</html>
CSS
• Cascading Style sheets
• Describes presentation of a document
• Separates doc content from presentation
• Introduced in 1996, about 2/3 pages in 2008
<html>
<head>
<style>
body {font-size:100%;}
h1 {font-size:2.5em;}
</style>
</head>
<body>
<h1>This is heading 1</h1>
</body>
</html>
HTTPS
• HTTP is sent plain text; unsecured
• HTTP subject to man-in-the-middle and
eavesdropping attacks
• HTTPS = HTTP + SSL/TLS protocol
• Secure channel over an insecure network
• Relies on server certificates/authorities
• Developed in 1994 by Netscape
Security
• Malware, identity theft, fraud, espionage
• 1 in 10 pages may contain malicious code
• SQL injection
• Cross-site scripting (XSS), 70% vulnerable
• Phishing
Statistics
• At least 13.15 billion pages
• Over 1 trillion unique URLs
• As of May 2009, over 109.5 million websites
• 74% are in .com domain
Statistics
Google Statistics
Questions/Suggestions?
• Elena Silenok
• [email protected], twitter: @silenok
• Charlie Robbins
• [email protected], twitter: @nodejitsu
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