HTML,

HTML, an initialism of HyperText Markup Language, is the predominant markup language for web pages. It provides a means to describe the structure of text-based information in a document — by denoting certain text as links, headings, paragraphs, lists, and so on — and to supplement that text with interactive forms, embedded images, and other objects. HTML is written in the form of tags, surrounded by angle brackets. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code (such as JavaScript) which can affect the behavior of Web browsers and other HTML processors.

HTML is also often used to refer to content of the MIME type text/html or even more broadly as a generic term for HTML whether in its XML-descended form (such as XHTML 1.0 and later) or its form descended directly from SGML (such as HTML 4.01 and earlier).

By convention, html format data files use a file extension .html or .htm.





What is HTML
HTML is a simple, universal mark-up language that allows Web publishers to create complex pages of text and images that can be viewed by anyone else on the Web, regardless of what kind of computer or browser is being used.
All you really need to create Web pages is a simple text editor and a basic understanding of HTML. To put your files on the Web, you will need an ftp client like WS_FTP LE for Windows, or Fetch for Mac. These are free downloads for students and will let you connect to a server, where you will store your files. Software like Dreamweaver or GoLive have FTP capabilities built in. (See How to FTP).

HTML is just a series of tags that are integrated into a text document. They're a lot like stage directions - silently telling the browser what to do, and what props to use.

What are HTML tags?
HTML tags tell a browser how to display information. Users of word processors were once required to type control-b to start bolding text and then control-b to stop bolding. Likewise, HTML tags usually (but not always) consist of a pair of tags that "turn on" and then "turn off" directions to affect text display.

HTML tags are usually English words (such as blockquote) or abbreviations (such as "p" for paragraph), but they are distinguished from the regular text because they are placed in small angle brackets. So the paragraph tag is <p>, and the blockquote tag is <blockquote>. Some tags dictate how the page will be formatted (for instance, <p> begins a new paragraph), and others dictate how the words appear (<b> makes text bold).

When you open a tag- say <blockquote> - you must also close it off with another tag - in this case, </blockquote>. Note the slash - / - before the word "blockquote"; that's what distinguishes a closing tag from an opening tag.

Example use of bold tag How it will display
<b>I'm bold</b> I'm bold
This will <b>bold</b> one word. This will bold one word.


HTML markup
HTML markup consists of several key components, including elements (and their attributes), character-based data types, and character references and entity references. Another important component is the document type declaration.

Elements
Elements are the basic structure for HTML markup. Elements have two basic properties: attributes and content. Each attribute and each element's content has certain restrictions that must be followed for an HTML document to be considered valid. An element usually has a start tag (e.g. <element-name>) and an end tag (e.g. </element-name>). The element's attributes are contained in the start tag and content is located between the tags (e.g. <element-name attribute="value">Content</element-name>). Some elements, such as <br>, do not have any content and must not have a closing tag. Listed below are several types of markup elements used in HTML.

Structural markup describes the purpose of text. For example, <h2>Golf</h2> establishes "Golf" as a second-level heading, which would be rendered in a browser in a manner similar to the "HTML markup" title at the start of this section. Structural markup does not denote any specific rendering, but most Web browsers have standardized on how elements should be formatted. Text may be further styled with Cascading Style Sheets (CSS).


Presentational markup describes the appearance of the text, regardless of its function. For example <b>boldface</b> indicates that visual output devices should render "boldface" in bold text, but gives no indication what devices which are unable to do this (such as aural devices that read the text aloud) should do. In the case of both <b>bold</b> and <i>italic</i>, there are elements which usually have an equivalent visual rendering but are more semantic in nature, namely <strong>strong emphasis</strong> and <em>emphasis</em> respectively. It is easier to see how an aural user agent should interpret the latter two elements. However, they are not equivalent to their presentational counterparts: it would be undesirable for a screen-reader to emphasize the name of a book, for instance, but on a screen such a name would be italicized. Most presentational markup elements have become deprecated under the HTML 4.0 specification, in favor of CSS based style design.



Hypertext markup links parts of the document to other documents. HTML up through version XHTML 1.1 requires the use of an anchor element to create a hyperlink in the flow of text: <a>Wikipedia</a>. However, the href attribute must also be set to a valid URL so for example the HTML code, <a href="http://en.wikipedia.org/">Wikipedia</a>, will render the word "Wikipedia" as a hyperlink.To link on an image, the anchor tag use the following syntax: <a href="url"><img src="image.gif"></a>


Attributes
Most of the attributes of an element are name-value pairs, separated by "=", and written within the start tag of an element, after the element's name. The value may be enclosed in single or double quotes, although values consisting of certain characters can be left unquoted in HTML (but not XHTML).[14][15] Leaving attribute values unquoted is considered unsafe.[16] In contrast with name-value pair attributes, there are some attributes that affect the element simply by their presence in the start tag of the element[17] (like the ismap attribute for the img element[18]).

Most elements can take any of several common attributes:

The id attribute provides a document-wide unique identifier for an element. This can be used by stylesheets to provide presentational properties, by browsers to focus attention on the specific element, or by scripts to alter the contents or presentation of an element.
The class attribute provides a way of classifying similar elements for presentation purposes. For example, an HTML document might use the designation class="notation" to indicate that all elements with this class value are subordinate to the main text of the document. Such elements might be gathered together and presented as footnotes on a page instead of appearing in the place where they occur in the HTML source.
An author may use the style non-attributal codes presentational properties to a particular element. It is considered better practice to use an element’s son- id page and select the element with a stylesheet, though sometimes this can be too cumbersome for a simple ad hoc application of styled properties.
The title attribute is used to attach subtextual explanation to an element. In most browsers this attribute is displayed as what is often referred to as a tooltip.
The generic inline element span can be used to demonstrate these various attributes:

<span id="anId" class="aClass" style="color:blue;" title="Hypertext Markup Language">HTML</span>
This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language."

Most elements also take the language-related attributes lang and dir





Data types
HTML defines several data types for element content, such as script data and stylesheet data, and a plethora of types for attribute values, including IDs, names, URIs, numbers, units of length, languages, media descriptors, colors, character encodings, dates and times, and so on. All of these data types are specializations of character data.



Hypertext features not in HTMLHTML lacks some of the features found in earlier hypertext systems, such as typed links, transclusion, source tracking, fat links, and more.[20] Even some hypertext features that were in early versions of HTML have been ignored by most popular web browsers until recently, such as the link element and in-browser Web page editing.

Sometimes Web services or browser manufacturers remedy these shortcomings. For instance, wikis and content management systems allow surfers to edit the Web pages they visit.