Hypertext refers to the ability to move among information in many files in non-linear way by activing links to other files.
HTML is a subset of a larger language called SGML (Standard General Markup Language). SGML has many other markup language subsets, including XML(eXtensible Markup Language) and XHTML (which combines XML and HTML).
This is a job typically done by Web browsers. It is referred to as rendering the HTML. Web browsers include: Internet Explorer (IE), Firefox, Mozilla, Safari, Konqueror, Opera, Neoplanet.
An HTML page can be viewed as a file on the local computer, or more commonly as a paged created by a server at some internet site. Normally an HTML file uses has one of the two suffixes .html or .htm. On MS Windows, files with these suffixes are typically associated with IE and so one just double-clicks on the file to have IE render it.
When accessed by an internet server, the page is identified by a URL (Universal Resouce Locator) of the formprotocol://server/itemThe item need not be present or can be a series of subitems separated by slashes (/). For example
http://www.google.com http://www.cs.wcupa.edu/~rkline/csw131
The www.google.com and www.cs.wcupa.edu are actual servers which listen for connections from browser clients. The http part is the protocol (HyperText Transfer Protocol in this case) which indicates how the web browser should connect with the server.
There are a number of web server programs in use, but the dominant ones are Apache (an open source program which runs on multiple operating systems) and IIS (Internet Information Services), which runs on Microsoft Windows platforms.
The final item in a URL part usually indicates a specific file or directory on the server. If the item is a not a file a certain default file is served.The actual file which accessed by a server may be a program which generates HTML code instead of static file. This is referred to server-side Web programming. Again, there are many programming languages which effect server-side programming including: ASP (Active Server Pages), PHP, Perl/CGI, JSP, etc.
The web browser can also access other types services on computers, such as FTP (File Transfer Protocol). It is indicated by the protocol line starting withftp://Even files on a local computer have a URL. The protocol used is called the file protocol, e.g.,
file://C:\Documents and Settings\user\Desktop\testing.html
<h2>Welcome to My Page</h2> This is a <b>bold</b> thing to say. This is an <em>emphatic</em> thing to say. Here's a link to <a href="http://www.google.com">Google</a>.Output:
This is a bold thing to say.
This is an emphatic thing to say.
Here's a link to Google.
| start tag: | <element attr1="value1" attr2="value2" ... > |
| end tag: | </element> |
| complete tag: | <element attr1="value1" attr2="value2" ... /> |
For the most part, HTML elements are used in pairs: a start tag followed later by an end tag; example elements include: p, h1, i, b. Examples of complete elements (which use no end tag) are br, hr, img. The terms tag and element although slightly different are often used interchangeably.
The element name is case-insensitive (i.e. TABLE, Table, and table are all equivalent), but, by conformance with XHTML standards, it is preferred that the element name be in lower case.
The attributes attr1, etc. further quantify how an element behaves. Attributes should always have a quoted value, but regular HTML permits attributes without values.
Style Sheets refer to sets of style rules which can be generated separately and applied to HTML elements with little change in the element tag. These style rules specify common properties dealing with fonts, colors, alignments, margins, etc.
The creation of style rules was done to allow an HTML document to separate into a content portion (the document) and the style rules so that one could more easily adjust style features without having to edit the actual document.The XML language is a markup language used to describe data in a hierarchical way. It express the content of a document without any notion of how the data in the document might be rendered into a browser.
Unlike HTML, the XML language is more strict in its syntax. In HTML the starting/ending tags are not strictly enforced and can function often even when not nested properly, for example, both of these create the desired effect in HTML, although the latter is syntactically incorrect (from both HTML and XHTML perspectives):(1) Here is a bold, emphatic word: <b><em>STOP</em></b> (2) Here is a bold, emphatic word: <b><em>STOP</b></em>These two lists represent correct HTML syntax, but the latter one is not correct with respect to XHTML, since the closing li tags are missing.
(1) Here is a list: <ul> <li>one</li> <li>two</li> </ul> (2) Here is a list: <ul> <li>one <li>two </ul>Another type of XHTML error is represented below. The latter is incorrect in XHTML but OK in HTML:
(1) First Line<br />Second Line (2) First Line<br>Second LineXHTML is a language which extends HTML and incorporates XML features along with the strict XML syntax rules. For example, the examples numbered (2) would not be accepted by XHTML.
As the result of the explosion of HTML usage new specifications of HTML have resulted in older tags and attributes going "out of favor" to be replaced by a better idea while many of the older tags are in extensive use.
The technical term for "being out of favor" is deprecated. It means that that the recent specifications no longer support or deem worthy of these tags and encourage authors to avoid them. The technical definition of deprecated can be seen in the official HTML specifications Nevertheless, browsers still continue to support them because much of the web content still use deprecated features. Indeed, many WYSIWYG HTML editors still generate deprecated features as well. Perhaps the most common deprecated tags are: font, center, the effects of both being generated through style properties.