HTML facts for kids

Quick facts for kids
HTML
(HyperText Markup Language)

The official logo of the latest version, HTML5
Filename extension	.html .htm
Internet media type	text/html
Type code	TEXT
Uniform Type Identifier (UTI)	public.html
Developed by	WHATWG World Wide Web Consortium (W3C; formerly)
Initial release	1993; 32 years ago (1993)
Latest release	Living Standard
Type of format	Document file format
Container for	HTML elements
Contained by	Web browser
Extended from	SGML
Extended to	XHTML
Open format?	Yes

HyperText Markup Language (HTML) is a markup language for creating webpages. Webpages are usually viewed in a web browser. They can include writing, links, pictures, and even sound and video. HTML is used to mark and describe each of these kinds of content so the web browser can show them correctly.

HTML can also be used to add meta information to a webpage. Meta information is information about the web page. For example, the name of the person who made it. Meta information is not usually shown by web browsers.

Cascading Style Sheets (CSS) and JavaScript can be included in HTML code. CSS is used to change how a webpage looks. JavaScript is used to add features to webpages and make them more interactive.

HTML was made by the World Wide Web Consortium (W3C). There are many versions of HTML. The current standard is HTML 5.2. So, it is the version the W3C recommends. The W3C also develops XHTML. This is another markup language which is very similar to HTML, but more strict.

HTML version timeline

HTML 2

November 24, 1995

HTML 2.0 was published as RFC 1866. Supplemental RFCs added capabilities:

• November 25, 1995: RFC 1867 (form-based file upload)
• May 1996: RFC 1942 (tables)
• August 1996: RFC 1980 (client-side image maps)
• January 1997: RFC 2070 (internationalization)

HTML 3

January 14, 1997

HTML 3.2 was published as a W3C Recommendation. It was the first version developed and standardized exclusively by the W3C, as the IETF had closed its HTML Working Group on September 12, 1996.

Initially code-named "Wilbur", HTML 3.2 dropped math formulas entirely, reconciled overlap among various proprietary extensions and adopted most of Netscape's visual markup tags. Netscape's blink element and Microsoft's marquee element were omitted due to a mutual agreement between the two companies. A markup for mathematical formulas similar to that of HTML was standardized 14 months later in MathML.

HTML 4

December 18, 1997

HTML 4.0 was published as a W3C Recommendation. It offers three variations:

• Strict, in which deprecated elements are forbidden
• Transitional, in which deprecated elements are allowed
• Frameset, in which mostly only frame related elements are allowed.

Initially code-named "Cougar", HTML 4.0 adopted many browser-specific element types and attributes, but also sought to phase out Netscape's visual markup features by marking them as deprecated in favor of style sheets. HTML 4 is an SGML application conforming to ISO 8879 – SGML.

April 24, 1998

HTML 4.0 was reissued with minor edits without incrementing the version number.

December 24, 1999

HTML 4.01 was published as a W3C Recommendation. It offers the same three variations as HTML 4.0 and its last errata were published on May 12, 2001.

May 2000

ISO/IEC 15445:2000 ("ISO HTML", based on HTML 4.01 Strict) was published as an ISO/IEC international standard. In the ISO, this standard is in the domain of the ISO/IEC JTC 1/SC 34 (ISO/IEC Joint Technical Committee 1, Subcommittee 34 – Document description and processing languages).

After HTML 4.01, there were no new versions of HTML for many years, as the development of the parallel, XML-based language XHTML occupied the W3C's HTML Working Group.

HTML 5

October 28, 2014

HTML5 was published as a W3C Recommendation.

November 1, 2016

HTML 5.1 was published as a W3C Recommendation.

December 14, 2017

HTML 5.2 was published as a W3C Recommendation.

Markup

HTML markup consists of several key components, including those called tags (and their attributes), character-based data types, character references and entity references. HTML tags most commonly come in pairs like <h1> and </h1>, although some represent empty elements and so are unpaired, for example <img>. The first tag in such a pair is the start tag, and the second is the end tag (they are also called opening tags and closing tags).

Another important component is the HTML document type declaration, which triggers standards mode rendering.

The following is an example of the classic "Hello, World!" program:

<!DOCTYPE html>
<html>
  <head>
    <title>This is a title</title>
  </head>
  <body>
    <div>
        <p>Hello world!</p>
    </div>
  </body>
</html>

The text between <html> and </html> describes the web page, and the text between <body> and </body> is the visible page content. The markup text <title>This is a title</title> defines the browser page title shown on browser tabs and window titles and the tag <div> defines a division of the page used for easy styling. Between <head> and </head>, a <meta> element can be used to define webpage metadata.

The Document Type Declaration <!DOCTYPE html> is for HTML5. If a declaration is not included, various browsers will revert to "quirks mode" for rendering.

Elements

HTML element content categories

HTML documents imply a structure of nested HTML elements. These are indicated in the document by HTML tags, enclosed in angle brackets.

In the simple, general case, the extent of an element is indicated by a pair of tags: a "start tag" <p> and "end tag" </p>. The text content of the element, if any, is placed between these tags.

Tags may also enclose further tag markup between the start and end, including a mixture of tags and text. This indicates further (nested) elements, as children of the parent element.

The start tag may also include the element's attributes within the tag. These indicate other information, such as identifiers for sections within the document, identifiers used to bind style information to the presentation of the document, and for some tags such as the <img> used to embed images, the reference to the image resource in the format like this: <img src="example.com/example.jpg">

Some elements, such as the line break <br> do not permit any embedded content, either text or further tags. These require only a single empty tag (akin to a start tag) and do not use an end tag.

Many tags, particularly the closing end tag for the very commonly used paragraph element <p>, are optional. An HTML browser or other agent can infer the closure for the end of an element from the context and the structural rules defined by the HTML standard. These rules are complex and not widely understood by most HTML authors.

The general form of an HTML element is therefore: <tag attribute1="value1" attribute2="value2">''content''</tag>. Some HTML elements are defined as empty elements and take the form <tag attribute1="value1" attribute2="value2">. Empty elements may enclose no content, for instance, the <br> tag or the inline <img> tag. The name of an HTML element is the name used in the tags. The end tag's name is preceded by a slash character /. If a tag has no content, an end tag is not allowed. If attributes are not mentioned, default values are used in each case.

Element examples

Header of the HTML document: <head>...</head>. The title is included in the head, for example:

<head>
  <title>The Title</title>
  <link rel="stylesheet" href="stylebyjimbowales.css"> 
</head>

Headings

HTML headings are defined with the <h1> to <h6> tags with H1 being the highest (or most important) level and H6 the least:

<h1>Heading level 1</h1>
<h2>Heading level 2</h2>
<h3>Heading level 3</h3>
<h4>Heading level 4</h4>
<h5>Heading level 5</h5>
<h6>Heading level 6</h6>

The effects are:

Heading Level 1

Heading Level 2

Heading Level 3

Heading Level 4

Heading Level 5

Heading Level 6

CSS can substantially change the rendering.

Paragraphs:

<p>Paragraph 1</p> <p>Paragraph 2</p>

Line breaks

<br>. The difference between <br> and <p> is that <br> breaks a line without altering the semantic structure of the page, whereas <p> sections the page into paragraphs. The element <br> is an empty element in that, although it may have attributes, it can take no content and it must not have an end tag.

<p>This <br> is a paragraph <br> with <br> line breaks</p>

Links

This is a link in HTML. To create a link the <a> tag is used. The href attribute holds the URL address of the link.

<a href="https://www.kiddle.co/">A link to Kiddle!</a>

Inputs

There are many possible ways a user can give inputs like:

<input type="text"> 
<input type="file"> 
<input type="checkbox">

Comments:

Comments can help in the understanding of the markup and do not display in the webpage.

There are several types of markup elements used in HTML:

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). Leaving attribute values unquoted is considered unsafe. 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, like the ismap attribute for the img element.

There are several common attributes that may appear in many elements :

• The id attribute provides a document-wide unique identifier for an element. This is used to identify the element so that stylesheets can alter its presentational properties, and scripts may alter, animate or delete its contents or presentation. Appended to the URL of the page, it provides a globally unique identifier for the element, typically a sub-section of the page. For example, the ID "Attributes" in https://en.wikipedia.org/wiki/HTML#Attributes.
• The class attribute provides a way of classifying similar elements. This can be used for semantic or presentation purposes. For example, an HTML document might semantically use the designation <class="notation"> to indicate that all elements with this class value are subordinate to the main text of the document. In presentation, 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. Class attributes are used semantically in microformats. Multiple class values may be specified; for example <class="notation important"> puts the element into both the notation and the important classes.
• An author may use the style attribute to assign presentational properties to a particular element. It is considered better practice to use an element's id or class attributes to select the element from within a stylesheet, though sometimes this can be too cumbersome for a simple, specific, or ad hoc styling.
• The title attribute is used to attach a subtextual explanation to an element. In most browsers this attribute is displayed as a tooltip.
• The lang attribute identifies the natural language of the element's contents, which may be different from that of the rest of the document. For example, in an English-language document:

  <p>Oh well, <span lang="fr">c'est la vie</span>, as they say in France.</p>

The abbreviation element, abbr, can be used to demonstrate some of these attributes:

<abbr id="anId" class="jargon" style="color:purple;" title="Hypertext Markup Language">HTML</abbr>

This example displays as HTML; in most browsers, pointing the cursor at the abbreviation should display the title text "Hypertext Markup Language."

Most elements take the language-related attribute dir to specify text direction, such as with "rtl" for right-to-left text in, for example, Arabic, Persian or Hebrew.

Incomplete list of HTML tags

Images for kids

• 

  Tim Berners-Lee in April 2009

See also

In Spanish: HTML para niños