HyperText Markup Language (HTML) & Extensible HyperText Markup Language (XHTML)

HTML is a language used to markup a text document with tags which describe how the document should look in a web browser. The language's power lies in the fact that it is interactive, cross-platform (Mac, DOS, UNIX, etc), multimedia and a client-server application as well. Though there is no regulatory body the World Wide Web Consortium (w3.org) oversees the development of HTML and other Internet languages and protocols.

Please note that this introduction to web development requires a good knowledge of computers and how they work.

The World Wide Web (WWW) is made up of billions of HTML documents stored on millions of computers worldwide.

When web pages or HTML documents are viewed by a visitor or client the web browser will format the document using the codes or markup tags and display it on the screen. How the document is displayed varies depending on a number of factors including the type of browser, the type of computer (monitor, video settings, resolution, etc), personal preference settings and the speed of the internet connection.

Web pages can be created in a text editor using the ASCII character set recognized by any modern computer. The Extended Character Set is used to add symbols and other characters to web pages. Non Roman based languages can also be created using a variety of other character sets though the visitor may need to download and install additional software to view documents created with these character sets. The UNICODE standard has addressed many of the issues involved with creating websites in a variety of languages.

Markup tags are defined by angle brackets < >. An HTML tag *must* have a beginning tag and an end tag. An example would be <b> begins to bold text and </b> ends bold text. Any text between the tags would be rendered as bold text by the readers browser. Tags are case insensitive (upper or lower are acceptable).

Note: Though there are tags that work without end tags the latest recommendations from the W3C is that developers use end tags none the less. If a tag doesn't have an end tag (<hr> for instance) the way to add an end tag is to add a space and slash before closing the tag ( e.g. <hr /> )

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HTML ignores white space, truncating any it finds to a single space. This includes tabs, line breaks, multiple space, etc.. All spaces must be inserted into an HTML document using tags.

A Document Type Definition (DTD) provides the browser agent with information about what type of document to display and a link to the DTD standards for comparison. An example of a DTD which tells the browser that the document is an XHTML transitional document would be:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

A web page begins with a Document Definition and has two sections; the head and body. An HTML document must begin with <html> and end with </html>. This tells the browser agent when the web page begins and ends so that it can begin displaying it.

The <head> tag contains the non-displaying document. As well as containing Meta tags used by search engines to categorize HTML documents, the head can also contain programming scripts, document formatting information such as stylesheets and language information. The web server reads the information in the head of the document before reading the information in the body. A character set definition is required to display the page properly.

The <body> tag contains the displaying document and determines how the document will display.

Because blank spaces are truncated into a single space it is necessary to define paragraphs and line breaks. Use the <p> and </p> to define a paragraph and use <br /> to set a line break. You can also use the <div> </div> container which has the characteristics of paragraph tag but with more options.

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