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WWW Information Pack
Topics covered: browsers, hyperlinks, URLs, client-server architecture, Internet Explorer, Netscape, Mozilla, Opera, adaptive browsers
A browser is simply a computer program that you use for obtaining and viewing web documents.
Because the web is evolving rapidly, new versions of browser software become available all the time. Ideally, a good web document should be able to be viewed by any browser... although in practice many older web browsers will struggle to display some modern web pages correctly.
Microsoft Internet Explorer version 6 (IE6) is currently the most widely-used web browser, and is recommended for use in the University computer classrooms at the time of writing. Unless otherwise stated, all illustrations and examples in these Factsheets will refer to IE6.
When you start IE6 in a University classroom, it will usually display the University's main home page. A home page (or index page) is the main "front door" into a set of related web pages, and will guide the user on to other subsidiary pages. A complete collection of related web pages (typically published by a single organisation) is commonly called a web site (or "website").
Figure 2.1 - Internet Explorer 6 displaying the University's home page
Some of the pieces of text on the University home page are intended to function as links to other pages. When you move your mouse over these links, the pointer will change to a small pointing hand. If you click the left mouse button (only once is necessary!) the browser’s display will change (there might be a delay of a few seconds before this happens), and you should now see a new web page. You have now followed a hyperlink, from one web page to another.
Figure 2.2 - Clicking once on the Staff link (left) will cause the browser to load the corresponding web page (right)
Pictures, as well as text, can function as links. The University logo at the top-left of many departmental web pages will usually function as a link back to the main University home page.
Figure 2.3 - The
button, and its convenient drop-down list of recently-visited pages
You may have come across references to specific web pages, which look something
like this:
http://www.abdn.ac.uk/web/
This is the "address" of a specific piece of information on the web. Technically, it is called a URL (or Uniform Resource Locator).
To go directly to this page, simply type the URL (or copy-and-paste it) directly into the long box near the top of your browser window, and then press (i.e. the Carriage Return key).
Figure 2.4 - Entering a URL into the bar
Hopefully, the new web page should be loaded. This might take some time, particularly if the page is stored on a distant or busy computer.
A list of the URLs that you have typed in recently can be obtained by clicking on the small down-arrow to the right of the box.
It is useful to understand what is going on "behind the scenes" when you view a web page.
All web pages are stored on the hard disk of a computer, just like any other files. A computer which is dedicated to storing web pages and publishing them (i.e. making them available to the outside world) is called a server. Most Universities and large organisations now have their own web servers. Web pages published on a particular server are sometimes said to be hosted on that server.
Whenever you want to view a web page, the following things need to happen:
By requesting data from a server in this way, your browser is said to be acting as a client.
Figure 2.5 - The client/server interaction that underlies the World Wide Web.
This explains why some web pages can take a long time to load. Your browser has to contact another computer (often on the other side of the world), which must then send all the data back across the Internet to Aberdeen.
Having grasped the above concept of clients and servers, it becomes possible to interpret URLs more fully.
Consider this URL:
http://www.abdn.ac.uk/web/faq.hti
http stands for Hypertext Transfer Protocol - the set of rules by which the above client-server interaction takes place. Increasingly, the first http:// part of the URL is omitted when people quote URLs. Modern web browsers will assume that it was intended, and will automatically insert it for you. Some older types of Internet locations might require a prefix of something other than http:// but you are unlikely to encounter them in everyday use.
The next part of the URL identifies the web server that is hosting the requested page. In the currect example, www.abdn.ac.uk identifies the web server of the University of Aberdeen. The abdn.ac.uk part is technically known as a domain name. Any large organisation will usually have its own unique domain name, under which it will publish its own web site.
The subsequent parts of the URL identify the location of the particular page within the files stored on the hosting web server. In this example, we are requesting the page faq.hti which is stored inside the folder web on the University of Aberdeen web server.
Occasionally, you might encounter some URLs that are case-sensitive, so you will need to take care to enter the correct combination of upper-case and lower-case characters. For example, http://www.abdn.ac.uk/web/ will take you to the Web Design Unit pages, while http://www.abdn.ac.uk/WEB/ will not.
At times, you may fail to retrieve a web page. Here are two common causes:
The server which stores the web page that you are requesting might be unavailable, perhaps because it is temporarily "down" for maintenance, or because it has been removed from the web permanently. This can lead to error messages such as the following:
The page cannot be displayed
The page you are looking for is currently unavailable.
Cannot find server or DNS Error
DNS name lookup failure
In this case you should check that you typed the URL correctly (no extra dots, slashes or spaces), and perhaps try again later.
In this case you have made contact with the correct hosting server, but it cannot find the specific page that you have requested. Perhaps the page’s author has removed it, or changed its name. This can lead to error messages such as:
Missing page - Error 404
You have requested a page which is not available on this server.
Again you should check whether you have typed the URL correctly, and perhaps try again later. If you experience a '404' error when trying to follow a link from someone else’s web page, then it is quite likely that the source web page is rather old, and that its author has neglected to check that the links on it are all still valid. This is known as a broken link.
One useful trick is to see whether you can access any documents higher up
in the directory structure of the URL. For example, if you cannot retrieve
http://www.bbc.co.uk/radio4/science/physics.htm
then see if you can access:
http://www.bbc.co.uk/radio4/science/
or
http://www.bbc.co.uk/radio4/
As stated above, Microsoft Internet Explorer 6 is currently the recommended browser for general University use. However there are plenty of other browser programs in existence, many of which are designed to fulfil specialised needs. The web gives a lot of freedom to the user, to choose the browser software that they want to use, and also to customise the way in which that browser behaves. So there is never any single "correct" way of viewing a web page: the same page may look quite different when viewed in two different browsers.
This can make life very complicated for the potential web author, because they always have to consider how their pages will be displayed in a variety of different browsers. However, it is greatly to the advantage of the user, who is not "locked in" to any single proprietary browser or operating system. The web is essentially an "open" system - designed to be used by anybody from any type of computer.
Netscape dominated the Web browser market between 1995 and 1996, largely because it was the first browser to support innovative and visually appealing page layout features. Many Universities and public sector organisations installed Netscape version 4 for general use around 1998, at a time when its closest competitor (Microsoft's Internet Explorer) was afflicted by troublesome security flaws.
In more recent years, Microsoft's strategy of integrating Internet Explorer (IE) ever more fully into the Windows operating system has meant that many more people have started using IE. Although the legality of Microsoft's strategy was challenged by the US Department of Justice in a lengthy court case, the plan worked, and IE overtook Netscape as the most widely-used web browser.
Netscape 4 is now a very dated browser, and its continued use is discouraged. Although copies of it are still in use in various Universities, NHS Trusts and local authorities, its use outside the public sector is reputed to have declined to approximately 3 per cent (data from www.statmarket.com).
The major drawback of Netscape 4 is its very poor and incomplete support for a technology called Cascading Style Sheets (CSS), which is now a standard recommended technique for building web pages. Netscape 4 was developed at a time when CSS was still being planned, with the result than many CSS-based pages display very badly in it. An increasing proportion of web pages will simply look "broken" in Netscape 4.
In March 1998, Netscape decided to make the underlying code of its web browser publicly available, so that programmers anywhere in the world could collaborate freely and voluntarily to develop and improve future versions. This "Open Source" development strategy eventually came to fruition with the release of version 1 of Mozilla, in June 2002. Although its interface may appear superficially similar to Netscape, Mozilla is actually a considerably more advanced and stable browser than its predecessor. The community of Open Source developers have completely re-written the browser, making it much more compliant with modern web standards (including CSS). It includes some useful new features, such as the ability to prevent annoying "pop-up" advertising windows. In addition to versions for Windows and Macintosh, the Mozilla browser is also well-suited for use on the Linux operating system (which is itself built by the Open Source community).
Figure 2.6 - Mozilla is available from www.mozilla.org - you can read all about its development, and even view its full Open Source code at this site.
Opera is unusual because it is not free - a license costs US$39. However there is also a version containing embedded banner advertising, which you can download and use for free.
Figure 2.7 - Opera is available for Windows, Macintosh, Linux, and other systems at www.opera.com
To justify its license cost, Opera obviously needs to offer an advantage over its competition. Perhaps its major strength is its flexibility and friendliness to disabled users: you can browse through web pages and follow links with single key-strokes (rather than mouse-clicks); alternatively you can control the browser with a series of mouse movements (called gestures); an extremely useful "zoom" function enables you to magnify or reduce web pages, and you can work with several independently-functioning browser windows open at once, organised by a series of clickable "tabs". Opera has a good reputation for compliance with web standards such as CSS, and also claims to be "the fastest browser on earth" (a difficult claim to verify).
Figure 2.8 - Opera's zoom function allows you to magnify or reduce the displayed page
A number of browsers have been developed specifically for people with disabilities, visual impairment, reading difficulties, and other such special requirements. Some will convert the text of web pages into Braille, and others can read out the text of a web page through the computer's speakers, using a synthesised voice. Still others are designed to allow voice-driven navigation, so that the user can actually operate the browser by speaking to it.
An excellent list of links to such products is maintained by the Web Accessibility Initiative of the World Wide Web Consortium at www.w3.org/WAI/References/Browsing and further useful information may be obtained from a range of organisations such as AbilityNet www.abilitynet.org.uk and TechDis www.techdis.ac.uk.
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