What is the World Wide Web, how does it work? The World Wide Web (WWW) is part of the Internet, which itself is “a network of interconnected computers”, in other words the physical infrastructure used to transfer data (for example, emails, web documents etc.) between computers -What is the World Wide Web
The WWW is a body of virtual information stored on web servers. A web server is a computer system that runs software to allow people to look at the web pages stored on it from their own PCs.
What is the World Wide Web – The University has its own web server (even several) which is connected to the Joint Academic NETwork (JANET). From home, you have to connect (you must be registered first) to the web server of an Internet Service Provider (ISP) to access the Internet.
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What is the World Wide Web, how does it work? Publishing information on the web The HyperText Mark-up Language (X)HTML (HyperText Mark-up Language) is a document layout and hyperlink specification markup language used to format text and information for the web; it is NOT a programming language like C++ or Java.
(X)HTML consists of mark-up elements. The syntax of a typical element is as follows: <name attribute1=”value” attribute2=”value”>text</name>
At its most basic an (X)HTML element consists of an opening tag (<name>) and a closing tag (indicated by a forward slash before the tag name – </name>)containing text (or other elements).
Tags consist of a tag name and sometimes one or more optional attributes carrying values, which modify the default behaviour and settings of the tag.
(X)HTML elements instruct browsers (and other user agents such as screen readers) on how to render the content.
The best way to understand the syntax of tags is to look at a few examples: <h1>heading level 1</h1> – a level 1 heading <a href=”http://www.bristol.ac.uk”>University of Bristol</a> – a link to the University of Bristol homepage <table width=”80%” border=”1″ align=”center”><tr><td>Cell 1 Row 1</td></tr></table> – a table consisting of 1 row and 1 column A few (X)HTML elements do not contain anything, they either point to a resource (eg an image) or they insert an object (eg a line break, a line); these are called empty elements and they look like this: <name attribute1=”value” /> For example: <br /> – inserts a line break <hr size=”3″ width=”50%” noshade=”noshade” /> – inserts a horizontal rule
“Give me file x”
“Here it is” Desktop computer – “client”
Computer on the Internet holding information – remote “web server”
attribute value closing tag
<img src=”picture.jpg” width=”100″ height=”100″ alt=”picture of something” /> – inserts an image (X)HTML elements are the building blocks of the web. This means that (X)HTML is not going away.
Since 1990, HTML standards as defined by the World Wide Web Consortium (W3C, see
http://www.w3.org) have evolved considerably. Until recently, HTML 4.01 was the recommended standard, however it has been superseded by the eXtensible HyperText Mark-up Language (XHTML), which has now become the recommended standard.
Making the transition from HTML to XHTML is really easy. Except for a few differences, most of HTML is compliant with XHTML. In XHTML: • tags must be in lower case whereas HTML accepts UPPER as well as lower case; • attribute values must be enclosed in double quotes (for example, <td width=”120″> instead of <td width=120>); • elements must be correctly nested (for example, <strong><em>properly nested tags</em></strong> instead of <strong><em>incorrectly nested tags</strong></em>), • empty elements must be closed (for example, <hr /> instead of <hr>, <br /> instead of <br>), • all attributes must be given explicit values (for example, <hr noshade=”noshade” /> instead of <hr noshade>), (X)HTML files should be saved with the extension html rather than htm (eg welcome.html).