Web Development Techniques: 2011

HTML 2.0 (RFC 1866) was developed by the IETF's HTML Working Group, which closed in 1996 it set the standard for core HTML features based upon current practice in 1994. Note that with the release of RFC 2854, RFC 1866 has been obsolate and its current status is HISTORIC.

HTML 3.2 W3C's first Recommendation for HTML which represented the consensus on HTML features for 1996. HTML 3.2 added widely-deployed features such as tables, applets, text-flow around images, superscripts an subscripts, while providing backwards compatibility with the existing HTML 2.0 Standard.

HTML 4.0 First released as a W3C Recommendation on 18 December 1997. A second release was issued on 24 April 1998 with changes limited to editorial corrections. This specification has now been superseded by HTML 4.01.

The Most Important Differences:

XHTML elements must be properly nested
XHTML documents must be well-formed
Tag names must be in lowercase
All XHTML elements must be closed

Elements Must Be Properly Nested

In HTML some elements can be improperly nested within each other like this:

 This text is bold and italic 

In XHTML all elements must be properly nested within each other like this:

 This test is bold and italic 

Note: A common mistake in nested list, is to forget that the inside list mustbe within an element.

Documents Must Be Well-formed

All XHTML elements must be nested within the <html> root element. All other elements can have sub (children) elements. Sub elements must be in pairs and correctly nested within their parent element.

Tag Names Must Be In Lower Case

This is because XHTML documents are XML applications. XML is case-sensitive. Tags like and are interpreted as different tags.

This is wrong:

<BODY>

 This is a paragraph 

</BODY>

<html>

<head> ... </head>

<body> ... </body>

</html>

This is correct:

<body>

 This is a paragraph 

</body>

All XHTML Elements Must Be Closed

Non-empty elements must have an end tags.

This is Wrong:

 This is paragraph

 This is another paragraph

This is correct:

 This is a paragraph 

 This is another paragraph 

Empty Elements Must Also Be Closed

Empty elements must either have an end tag or the start tag must end with />

This is Wrong:

This is break 

Here comes a horizontal rule <hr>

Here's an image <img src="happy.gif" alt="Happy face">

This is Correct:

This is a break 

here comes a horizontal rule: <hr />

Here's an image <img src="happy.gif" alt="Happy face"/>

Mandatory XHTML Elements

All XHTML documents must have a DOCTYPE declaration. The html, head and body elements must be present, and the title must be present inside the head element.

This Is a Minimun XHTML document template:

<!DOCTYPE doctype goes here >

<html xmlns="http://www.w3.org/1999/xhtml">

<head>

<title> Title goes here </title>

</head>

<body>

Body text goes here

</body>

</html>

Note: The DOCTYPE declaration is not a part of the XHTML document itself. It is not an XHTML elements and it should not have a closing tag.

Note: The xmins attribute inside the <html> tag is required in XHTML. However, the validator on w3.org does not complain when this attribute is missing in an XHTML document. This is because "xmins=http://www.w3.org/1999/xhtml" is a fixed value and will be added to the <html> tag even if you do not include it.

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3.3. ASCII Entities with new Entity Names

Posted on 3:19 PM - by Dhanushka

3.4. ISO 8859-1 Symbol Entities

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3.2. HTML and ASCII

Posted on 3:17 PM - by Dhanushka

HTML uses standard 7-BIT ASCII when transmitting data over the Web. 7-BIT ASCII represents 128 different character values (0-127)

Hexadecimal values can be used to display non-standard letters and characters in browsers and plug-ins. HTML 4.01 supports the ISO 8859-1 (Latin-1) character set.

The lower part of ISO-8859-1 (codes from 0-127) is the original 7BIT ASCII standard. Most of these characters can be used without a character reference.

The higher part of ISO-8859-1 (codes from 160-255) can all be used using character entity names. Note that the entity names are case sensitive.

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3.1. The anatomy of an HTML Document

Posted on 3:06 PM - by Dhanushka

HTML is the lingua france for publishing hypertext on the World Wide Web. It is a non proprietary format based upon SGML, and can be created and processed by a wide range of tools, from simple plain text editors - you type it in from scratch - to sophisticated WYSIWYG authoring tools.

It is the base code for web pages.
It creates a visual presentation that is displayed by a web browser.

The commands in HTML coding (known as Tags) are enclosed in angel brackets < >. THe tags normally come as a set. One to open a command, and one to close it. Everything between the two tags will be affected by them. The closing tag uses a forward slash ( / ) in it.

< TAG NAME > </TAG NAME >

Tags are made up of elements, properties, and values. The command letters or words are called elements. Some ellements have declared settings called properties. These properties help describe or shape the way the element will work of function. The property settings are known as values. Some tags can have many properties, others have none.

<html>

<head>

<title> Welcome page </title>

</head>

<body>

Welcome to My Web Page

</body>

</html>

HEAD An introduction to the web page. In this area, some of the settings for the web page are introduced such as the TITLE, and information for search engines.

TITLE The title for the web page. This name will appear in the title bar at the top of the browser window. It is also used as the file name if someone 'bookmarks' your page or saves it. Typically, the TITLE should be a descriptive statement up to 200 characters.

BODY Main program section for web page. This is where it all happenes.

<html> tag - Language Attributes

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2.2. Common Browser Technologies

Posted on 3:05 PM - by Dhanushka

Internet Explorer

Internet Explorer (IE) by Microsoft is the most common Internet browser today. IE was Introduced in 1995 and passed Netscape in popularity in 1998.

Netscape

Netscape was the first commercial Internet browser. It was introduces in 1994. Netscape gradually Lost its popularity to Internet Explorer.

Mozilla

The Mozilla Project has grown from the ashes of Netscape. Browsers based on Mozilla code is the second largest browser family on the Internet today. represending about 30% of the Internet community.

Firefox

Firefox is a new browser from Mozilla. It was released in 2004 and has grown to be the second popular browser on the Internet.

Opera

Opera is another Internet browser. It is known to be fast and small, standards-compliant, and available for many operating systems. Opera is the Preferred browser for a number of small devices like mobile phones and hand-held computers.

2.2.1. Uniform Resource Identifier (URI)

A Unform Resource Identifier (URI), is a compact string of characters used to Identify or name a resource. the main purpose of this identification is to enable interaction with representations of the resource over a network, typically the World Wide Web, using specific protocols. URIs are defined in schemes defining a specific ayntax and associated protocols.

The URI syntax is essentially a URI scheme name like "HTTP" , "FTP" , "mailto" , "URN" . "tel" , "rtsp" , etc, followed by a colon character, and then a scheme-specifuc part. The syntax and semantics of the scheme-specific part are deremined by the specifications that govern the schemes, although the URI syntax does force all schemes to adhere to a certain generic syntax that, among other things, reserves certain characters for special purposes, without always saying what those purposes are. The URI syntax also enforces restrictions on the scheme-specific part, in order to, for example, provide for a degree of consistency when the part has hierarchical sructure.

URIs and URLs have a shared history. The idea of a URL - a short string representing a resource that is the target of hyperlink - was implicitly introduced in early 1990 in Tim Berners-Lee's proposals for HyperText. At the time, it was called a hypertext name or document name.

Examples of absolute URIs

http://somehost/absolute/URI/with/absolute/path/to/resource.txt
ftp://somehost/resource.txt

Examples of URI references

http://example/resource.txt#frag01
http://somehost/absolute/URI/with/absolute/path/to/resource.txt
/relative/URI/with/absolute.path/to/resource.txt
relative/path/to/resource.txt
../../../resource.txt
resource.txt
/resource.txt#frag01
#frag01

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2.1 The Idea of hypertext and hypermedia

Posted on 3:04 PM - by Dhanushka

HTML was devised as an easy means to format textual documents. HTTP is the method for delivering HTML documents. which the client browser then renders into an on-screen image.

HTML and HTTP were both invented bt Tim Berners-Lee, who was then working as a computer and networking specialist at a swiss research institute by the name of CERN. He wanted to give the Institute's researchers a simple markup language that would enable them to share their research papers via the internet. Berners-Lee based HTML onSGML, an international standard for marking uptext for presentation on a variety of physical devices. The basic idea of SGML is that the document's structure should be separated from its presentation.

To date, HTML has gone through four major standards, including the latest which is 4.01. In addition to HTML, Cascading Style Sheets (CSS) and Extensible Markup language (XML) have also provided a valuable contribution to the way of the web.

XHTML 1.0 is the latest standard for web doucuments. This standard infuses the HTML 4.01 standard with extensible language constructs courtesy of XML.

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1.3. Addressing and naming on the Internet

Posted on 3:04 PM - by Dhanushka

Internet Protocol Addressing

Each mchine connected to an IP network (such as the Internet) is addressed using a unique 32 bit number, the IP address.

Many machines will have more than one IP address - for example a machine running virtual websites will have an IP address for each website they host.

Other times a pool of IP addresses is shared between a number of machines - eg on a dynamic-IP dialup connection your machine will be allocated a different IP address each time you connect.

These addresses are usualy written in DOtted Quad notation (IPv4), as a series of four 8bit numbers, wrtten in decimal and separated by periods. For example 151.196.75.10.

Each number is in the range 0 to 255 - so if you ever see something that looks like an IP address with numbers outside those ranges it's not a real address.

Domain Name System

On the Internet, the Domain Name System (Dns) associates various sort of information with so-called domain names; most importanly, it serves as the "phone book" for the Internet; it translates human-readable computer hosatnames, into the IP addresses that networking wquipment needs for delivering information. it also stores other information such as the list of mail exchange servers that accept email for a given domain. In providing a worldwide keyword-based redirection service, the Domain Name System is an essential component of contemporary Internet use.

Parts of a domain name

A domain name usualy consists of two or more parts (technically labelss), separates by dots. for example Google.com

The rightmost label conveys the top-level domain
Each label to the left specifies a subdivision or subdomain of the domain above it Note that "subdomain" expresses relative dependence, not absolute dependence for example google.com. comprises a subdomain of the Com domain.
A hostname refer to a domain name that has one or more associated IP addresses.

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1.2. The Architecture of the Internet

Posted on 3:03 PM - by Dhanushka

The internet is by definition a meta-network, a constantly changin collection of thousand og individual networks intercommunicating with a common protocol.

The Internet architeccture is described in its name, a short form of the compound word "Inter-networking". This architecture is based in the very specification of the standard TCP/IP protocol, designed to connect any two networks which may be very different in internal hardware, software and technical design. Once two networks are interconnected, communication with TCP/IP is enabled end-to-end, so that any node on the Internet has the near magical ability to communicate with any other no matter where they are. This openness of design has enabled the Internet architecture to grow to a global scale.

In practice, the internet technical architecture looks a bit like a multi-dimensional river system, with small tributaries feeding medium-sized streams feeding large rivers. For example, an individual's access to the internet as often from home over a modem to a local internet service provider who connects to a regional network connected to a national network. At the office, a desktop computer might be connected to a local area network with a company connection to a corporate internet connected to several national Internet service providers. In genaral small local Internet service providers connect to medium-sized regional networks which connect to a large national networks, which then connect to a very large bandwidth networks on the Internet backbone. MOst Internet service providers have several redundant network cross-connections to other providers in order to ensure continuous availability.

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Contents

3.5.HTML to XHTML

3.3. ASCII Entities with new Entity Names

3.2. HTML and ASCII

3.1. The anatomy of an HTML Document

2.2. Common Browser Technologies

2.1 The Idea of hypertext and hypermedia

1.3. Addressing and naming on the Internet

1.2. The Architecture of the Internet

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