Web browsers

• let you see/navigate web pages,
• provide multimedia features,
• provide FTP and web-based E-mail.

Examples: Microsoft Internet Explorer (current version 6.0), Netscape Navigator (currently 7.1), Mozilla, Opera, Konqueror, Lynx, Arachne.

URI: The address of any resource either on the web or on a personal computer system.

URL: A URI of anything that is on the WWW. It must include a protocol (usually http://).

Home page: The first (main) page of a website.

Deep URL: A URL that includes a path into folders/files of a site e.g. www.mysite.com/exercises/test1.htm

Absolute URL: The full path from the domain server (i.e. from the www in the address onwards), as opposed to a ...

Relative URL: which is a path referenced from the current position.

Browser operation:

• It breaks the URL into the protocol (http://), the server + domain name (www.mysite.com) and the file requested (index.html, if no other file is specified).
• It communicates with the DNS to translate the address into an IP dotted quad.
• It uses the IP address to connect with the mysite web server.
• It uses HTTP to request the file from the server.

Authentication: Verifying a user's identity

• Anonymous login - No username or password required.
• Basic login - Username and password required, but request transmitted in plain text (unencrypted).
• Secure login - User name and password required, encrypted before being transmitted.
• Digital Certificates

Encryption: Turning a message into a form so that it can only be understood by someone who possesses the correct key.

The Challenge Handshake Authentication Protocol (CHAP):

• This is used to authenticate a source in a communication between two systems.
• The connecting system generates a random text string ("challenge phrase") and transmits it.
• The destination system sends back a coded version of the challenge string created using hash coding.
• The connecting system compares the returned hash code with its own locally generated hash code of the same string.
• If they match, both systems are using the same hash code, so the destination is authentic!
• The procedure is repeated the other way round if the destination system wants to authenticate the source.

Microsoft have produced their own version: The Microsoft Challenge Handshake Authentication Protocol (MS-CHAP).

For a guide to SSL and Digital Certificates, see General Topics - Security.

Intranet: Network used solely within a company and only by its employees.

Extranet: An intranet with added access to selected users (e.g. Internet banking) with logins + passwords.

Webinar: A "web seminar". Training, often with a PowerPoint presentation, delivered over the WWW.

A pop-up window is one that appears behind the browser when accessing certain pages.

• It displays when the current window is closed.
• They are irritating (often adverts), so many browsers allow you to block them.

Browser cache: (pronounced "cash") - a folder on your computer that stores recently/often visited web pages.

• Improve efficiency. Browser automatically checks the cache when a page is requested. If present, it is loaded from the cache, not the WWW.
• Cache can be set up to check for newer versions of pages regularly.

Cookies: small text files stored by web sites on your computer.

• Describe your actions, shopping habits, preferences etc.
• Accessed by the creating site to save you having to enter personal details (e.g. user names)
• Can be used maliciously to gather details about you for marketing etc.

Privacy issues with cookies:

• Only stored on your computer if you register with the creating site, so not the same as viruses etc.
• Browsers offer the ability to block all cookies (high privacy level) or some cookies (medium/low privacy).
• Browsers offer the ability to delete cookies - but your favourite sites will not immediately recognise you!
• Look at a company's privacy statement to see how it uses cookie information.

Proxy servers: Additional servers set up by companies to act as "middlemen" between their corporate servers and the web.
Functions of proxies are

• Security. The proxy replaces IP address of main server with its own, so "hiding" real server from the web. Can provide corporate firewall access to block unwanted traffic.
• Web document caching. Stores recently/frequently viewed pages like a cache to improve efficiency.

Troubleshooting client Internet problems:

Problem	Things to try
Unreadable text	Adjust font settings to compensate for low-resolution monitors.
Slow connection	Increase browser cache, increase frequency browser checks for updates, disable image loading.
No connections	If computer uses a proxy server, check browser is configured to work with it.
No images appear	Check if loading has been disabled. Turn it on with Show Pictures checkbox.
Slow browser	Is the browser too large? Try emptying it and reseting its size?

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