Introduction

The HyperText Markup Language (HTML) is a simple data format used to create hypertext documents that are portable from one platform to another. HTML documents are SGML documents with generic semantics that are appropriate for representing information from a wide range of domains.

As HTML is an application of SGML, this specification assumes a working knowledge of [SGML].

Scope

HTML has been in use by the World-Wide Web (WWW) global information initiative since 1990. Previously, informal documentation on HTML has been available from a number of sources on the Internet. This specification brings together, clarifies, and formalizes a set of features that roughly corresponds to the capabilities of HTML in common use prior to June 1994. A number of new features to HTML are being proposed and experimented in the Internet community.

This document thus defines a HTML 2.0 (to distinguish it from the previous informal specifications). Future (generally upwardly compatible) versions of HTML with new features will be released with higher version numbers.

HTML is an application of ISO Standard 8879:1986 Information Processing Text and Office Systems; Standard Generalized Markup Language (SGML). The HTML Document Type Definition (DTD) is a formal definition of the HTML syntax in terms of SGML.

This specification also defines HTML as an Internet Media Type[IMEDIA] and MIME Content Type[MIME] called `text/html’. As such, it defines the semantics of the HTML syntax and how that syntax should be interpreted by user agents.

Conformance

This specification governs the syntax of HTML documents and aspects of the behavior of HTML user agents.

Documents

A document is a conforming HTML document if:

• It is a conforming SGML document, and it conforms to the HTML DTD (see section HTML DTD). (1)
• It conforms to the application conventions in this specification. For example, the value of the HREF attribute of the A element must conform to the URIsyntax.
• Its document character set includes [ISO-8859-1] and agrees with [ISO-10646]; that is, each code position listed in section The HTML Coded Character Set is included, and each code position in the document character set is mapped to the same character as [ISO-10646] designates for that code position. (2)

Feature Test Entities

The HTML DTD defines a standard HTML document type and several variations, by way of feature test entities. Feature test entities are declarations in the HTML DTD that control the inclusion or exclusion of portions of the DTD.

HTML.Recommended

Certain features of the language are necessary for compatibility with widespread usage, but they may compromise the structural integrity of a document. This feature test entity selects a more prescriptive document type definition that eliminates those features. It is set to `IGNORE’ by default. For example, in order to preserve the structure of a document, an editing user agent may translate HTML documents to the recommended subset, or it may require that the documents be in the recommended subset for import.

HTML.Deprecated

Certain features of the language are necessary for compatibility with earlier versions of the specification, but they tend to be used and implemented inconsistently, and their use is deprecated. This feature test entity enables a document type definition that allows these features. It is set to `INCLUDE’ by default. Documents generated by translation software or editing software should not contain deprecated idioms.

User Agents

An HTML user agent conforms to this specification if:

• It parses the characters of an HTML document into data characters and markup according to [SGML]. (3)
• It supports the `ISO-8859-1′ character encoding scheme and processes each character in the ISO Latin Alphabet No. 1 as specified in section The HTML Document Character Set. (4)
• It behaves identically for documents whose parsed token sequences are identical. For example, comments and the whitespace in tags disappear during tokenization, and hence they do not influence the behavior of conforming user agents.
• It allows the user to traverse (or at least attempt to traverse, resources permitting) all hyperlinks from A elements in an HTML document.

An HTML user agent is a level 2 user agent if, additionally:

• It allows the user to express all form field values specified in an HTML document and to (attempt to) submit the values as requests to information services.

There are several articles that list some important upcoming features of HTML5, which can work on certain browsers. This tutorial for the web developer will show you how you can use certain features of HTML 5 NOW!

HTML 5 features which are useful right now include:

• Web Workers: Certain web applications use heavy scripts to perform functions. Web Workers use separate background threads for processing and it does not effect the performance of a web page.
• Video: You can embed video without third-party proprietary plug-ins or codec. Video becomes as easy as embedding an image.
• Canvas: This feature allows a web developer to render graphics on the fly. As with video, there is no need for a plug in.
• Application caches: Web pages will start storing more and more information locally on the visitor’s computer. It works like cookies, but where cookies are small, the new feature allows for much larger files. Google Gears is an excellent example of this in action.
• Geolocation: Best known for use on mobile devices, geolocation is coming with HTML5.

Advantages:

• Size of the files are compact in compared to other interactional media like Flash or Shockwave, and it downloads faster.
• It is supported by big browser manufacturers like Microsoft and Netscape.
• Highly flexible and easy to make changes.
• Viewer requires no extra plug-ins for browsing through the webpage that uses DHTML, they do not need any extra requirements or special software to view it.
• User time is saved by sending less number of requests to the server. As it is possible to modify and replace elements even after a page is loaded, it is not required to create separate pages for changing styles which in turn saves time in building pages and also reduces the number of requests that are sent to the server.
• It has more advanced functionality than a static HTML. it is capable of holding more content on the web page at the same time.

Disadvantages:

• It is not supported by all the browsers. It is supported only by recent browsers such as Netscape 6, IE 5.5, and Opera 5 like browsers.
• Learning of DHTML requires a lot of pre-requisites languages such as HTML, CSS, JS, etc should be known to the designer before starting with DHTML which is a long and time-consuming in itself.
• Implementation of different browsers are different. So if it worked in one browser, it might not necessarily work the same way in another browser.
• Even after being great with functionality, DHTML requires a few tools and utilities that are some expensive. For example, the DHTML text editor, Dreamweaver. Along with it the improvement cost of transferring from HTML to DHTML makes cost rise much higher.

Difference between HTML and DHTML:

• HTML is a markup language while DHTML is a collection of technologies.
• HTML is used to create static webpages while DHTML is capable of creating dynamic webpages.
• DHTML is used to create animations and dynamic menus but HTML not used.
• HTML sites are slow upon client-side technologies whereas DHTML sites are comparatively faster.
• Web pages created using HTML are rather simple and have no styling as it uses only one language whereas DHTML uses HTML, CSS, and Javascript which results in a much better and way more presentable webpage.
• HTML cannot be used as server side code but DHTML used as server side code.
• DHTML needs database connectivity but not in case of HTML.
• Files in HTML are stored using .htm or .html extension while DHTML uses .dhtm extension.
• HTML requires no processing from the browser but DHTML does.

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.

Document type declaration

HTML documents are required to start with a Document Type Declaration (informally, a “doctype”). In browsers, the doctype helps to define the rendering mode—particularly whether to use quirks mode.

The original purpose of the doctype was to enable parsing and validation of HTML documents by SGML tools based on the Document Type Definition (DTD). The DTD to which the DOCTYPE refers contains a machine-readable grammar specifying the permitted and prohibited content for a document conforming to such a DTD. Browsers, on the other hand, do not implement HTML as an application of SGML and by consequence do not read the DTD.