The World Wide Web CSCE 101 – Spring 2010
- 1. The World Wide Web CSCE 101 – Spring 2010
- 2. The Internet and the Web Internet: A worldwide computer network that connects hundreds of thousands of smaller networks. “The mother of all networks”. World Wide Web: The interconnected system of servers that support multimedia documents, i.e. the multimedia part of the Internet. Timeline: Early 1960s: introduction of the network concept 1970: ARPANET, scholarly-aimed networks 62 computers in 1974 500 computers in 1983 28,000 computers in 1987 1975: Ethernet developed by Robert Metcalf 1980: TCP/IP 1982: The first computer virus, Elk Cloner, spread via Apple II floppy disks 1989: Web invented by Tim Berners-Lee 1990: First Web browser based on HTML developed by Berners-Lee Early 1990s: Anderseen developed the first graphical browser (Mosaic) 1993: The White House launches its Web site
- 3. Web Browsers Web Browser: is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. Software that enables users to view Web pages and to jump from one page to another, e.g. IE, Mozilla Firefox, Safari, etc. Which browser is better? Why? Web Page: A document on the Web that can include multimedia data Web Site: A collection of related Web pages usually designed or controlled by the same individual or company. Generally shares a common domain name. Practical Browser Tools: Status Bar: security info, page load progress Favorites (bookmarks) View Source: view the code of a Web page Tools Internet Options history, temporary Internet files, home page, auto complete, security settings, programs, etc.
- 4. Domain Names URL (Uniform Resource Locator): The human-friendly address of a Web page String of characters that points to a piece of information on the Internet Syntax: protocol://domain name/directory/file, e.g. http://www.sc.edu/~hanczary/lectures.html The domain name includes the domain type and sometimes a country extension Have you ever mistyped a URL and gone to a website you weren’t expecting? ICANN non-profit organization was established to regulate human-friendly domain names DNS (Domain Name System): A distributed set of servers storing domain information in hierarchical fashion DNS provides the mapping between the IP addresses and URLs of Internet sites DNS requires static IP addresses DNS poisoning Domain names must be registered to ensure uniqueness, registration fees vary, cybersquatting
- 5. Domain Names Main Domain Extension Types Suffix Extension Descriptions .com ( .com mercial) is a generic top-level domain. It was one of the original top-level domains, and has grown to be the largest in use. .org ( .org anization) is a generic top-level domain, and is mostly associated with non-profit organizations. It is also used in the charitable field, and used by the open-source movement. Government sites and Political parties in the US have domain names ending in .org .net ( .net work) is a generic top-level domain and is one of the original top-level domains. Initially intended to be used only for network providers (such as Internet service providers). It is still popular with network operators, it is often treated as a second .com. It is currently the third most popular top-level domain. .edu ( .edu cation) is the generic top-level domain for educational institutions, primarily those in the United States. One of the first top-level domains, .edu was originally intended for educational institutions anywhere in the world. Only post-secondary institutions that are accredited by an agency on the U.S. Department of Education's list of nationally recognized accrediting agencies are eligible to apply for a .edu domain. .info ( .info rmation) is a generic top-level domain intended for informative website's, although its use is not restricted. It is an unrestricted domain, meaning that anyone can obtain a second-level domain under .info. The .info was one of many extension(s) that was meant to take the pressure off the overcrowded .com domain. .gov ( .gov ernment) a generic top-level domain used by government entities in the United States. Other countries typically use a second-level domain for this purpose, e.g., .gov.uk for the United Kingdom. Since the United States controls the .gov Top Level Domain, it would be impossible for another country to create a domain ending in .gov. .biz (business) the name is a phonetic spelling of the first syllable of "business." A generic top-level domain to be used by businesses. It was created due to the demand for good domain names available in the .com top-level domain, and to provide an alternative to businesses whose preferred .com domain name which had already been registered by another.
- 6. Cookies Little text files left on your hard disk by some websites you visit Cookies are data not programs, they do not generate pop-ups or behave like viruses Can include your log-in name and browser preferences Can be convenient But they can be used to gather information about you and your browsing habits “ Third party” cookies: used by advertising companies to track users across multiple sites People share machines session-id-time 954242000 amazon.com/ session-id 002-4135256-7625846 amazon.com/ x-main eKQIfwnxuF7qtmX52x6VWAXh@Ih6Uo5H amazon.com/ ubid-main 077-9263437-9645324 amazon.com/ Sample Amazon.com cookie
- 7. E-mail E-mail Software and Carriers: Free Web-based e-mail services (e.g. Yahoo Mail) or bundled with software (e.g. MS Outlook) E-mail Privacy: How did they find my e-mail address? Can anyone read the content of my messages? What happens to my deleted e-mail messages? What are my rights? - None Basically Can anything be done to enhance e-mail privacy? E-mail Security: Dangers of attachments and HTML graphics Useful E-mail Tools: Mailing lists, filters (rules)
- 8. Deciphering Spam Spam: Unsolicited e-mail in the form of advertisements or chain letters. Waste of storage space, processing power, bandwidth, and time E-mail address spoofing, disposable e-mail addresses or anonymous re-mailers, and zombies are techniques used in spamming Email address harvesting Motives: Marketing Chain letters & hoaxes Malicious intent Theft of confidential information (e.g. phishing) Spam Filters: Pattern-based or content based Challenge-based Black & White list based. Fight back by reporting new spammers to www.abuse.net , www.spamhaus.org , or www.rahul.net/falk
- 9. Searching for Information Search engine databases are often compiled using software programs called spiders Spiders crawl through the Web, following links from one page to another Index the words on that site Indexing techniques Influencing search results (paid, malicious e.g. Google bombs), link rot If you publish an embarrassing web page and then take it down, is it REALLY gone? Guidelines to evaluate Web resources Should you trust information you find online? Does the information appear on a professional site maintained by a professional organization? Does the website authority appear to be legitimate? Is the website objective, complete, and current?
- 10. Search Engines Types of Search Engines: Human-organized: Documents are categorized by subject-area experts, smaller databases, more accurate search results, e.g. Open Directory, About Computer-created: Software spiders crawl the web for documents and categorize pages, larger databases, ranking systems, e.g. Google Hybrid: Combines the two categories above Metasearch or clustering: Direct queries to multiple search engines and cluster results, e.g. Copernic, Vivisimo, Mamma Topic-specific – e.g. WebMD Advanced Search Options: Searches for various information formats & types, e.g. image search, scholarly search Advanced query operators and wild cards ? (e.g. science? means search for the keyword “science” but I am not sure of the spelling) * (wildcard, e.g. comput* searches for keywords starting with “comput” combined with any word ending) x AND y (both terms must be present) x OR y (at least one of the terms must be present)
- 11. More Web Resources Wikis: A Wiki is a website on which authoring and editing can be done by anyone at anytime using a simple browser. Wikipedia, Wikimedia, Wikibooks, Citizendium, etc. Allow individuals to edit content to facilitate Accuracy concerns Internet Telephony (VoIP): Providers include Vonage, Verizon, Skype, etc. Uses the Internet to make phone calls, videoconference Long-distance calls are either very inexpensive or free Quality, security, and reliability concerns
- 12. More Web Resources Social Networks: MySpace, Facebook, Friendster, Orkut, etc. What are some features of today’s popular social networks? Anti-social networks? Social networks as “study groups”, Courses 2.0 Privacy and safety concerns Plagiarism in the Internet Age: In a recent survey, 60% of students revealed that they have cheated in the past Websites offering course material, e.g. coursehero.com, cheathouse.com Use of portable electronic devices for cheating Services used to combat cheating, e.g. turnitin.com
- 13. More Web Resources Instant messaging (IM) and real-time chat (RTC) software Multi-protocol IM clients (AIM) Web-based IM systems (Forum, chat room) Podcasting Blogs Blogger, Xanga, LiveJournal, etc. Microblog, vlog, photoblog, sketchblog, linklog, etc. Blog search engines Blogs and advertising, implications of ad blocking software Do bloggers have the same rights as journalists? Really Simple Syndication (RSS) FireAnt, i-Fetch, RSS Captor, etc. Built-in Web browser RSS features Search download.com for keyword: “RSS Readers”