HTML (Hypertext Markup Language) definition

Hypertext Markup Language, a standardized system for tagging text files to achieve font, color, graphic, and hyperlink effects on World Wide Web pages.

HTML (Hypertext Markup Language) is the set of markup symbols or codes inserted in a file intended for display on a World Wide Web browser page. The markup tells the Web browser how to display a Web page's words and images for the user. Each individual markup code is referred to as an element (but many people also refer to it as a tag). Some elements come in pairs that indicate when some display effect is to begin and when it is to end.

Headings

Permitted Context: %Body.ContentContent Model: %text

HTML defines six levels of headings. A heading element implies all the font changes, paragraph breaks before and after, and any white space necessary to render the heading. The heading elements are H1, H2, H3, H4, H5, and H6 with H1 being the highest (or most important) level and H6 the least. For example:

<H1>This is a top level heading</H1> Here is some text.<H2>Second level heading</H2> Here is some more text.

Use the DIV element together with header elements when you want to make the hierarchical structure of a document explicit. This is needed as header elements themselves only contain the text of the header, and do not imply any structural division of documents into sections. Header elements have the same content model as paragraphs, that is text and character level markup, such as character emphasis, inline images, form fields and math.

Headers play a related role to lists in structuring documents, and it is common to number headers or to include a graphic that acts like a bullet in lists. HTML 3.0 recognizes this with attributes that assist with numbering headers and allow authors to specify a custom graphic.

The numbering style is controlled by the style sheet, e.g.

1. The style sheet specifies whether headers are numbered, and which style is used to render the current sequence number, e.g. arabic, upper alpha, lower alpha, upper roman, lower roman or a numbering scheme appropriate to the current language.

2. Whether the parent numbering is inherited, e.g. "5.1.d" where 5 is the current sequence number for H1 headers, 1 is the number for H2 headers and 4 for H3 headers.

The seqnum and skip attributes can be used to override the default treatment of header sequence numbers, and provide for a continuity with numbered lists.

The dingbat or src attribute may be used to specify a bullet-like graphic to be placed adjacent to the header. The positioning of this graphic is controlled by the style sheet. The graphic is for decorative purposes only and silently ignored on non-graphical HTML user agents.

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Word Wrapping

User agents are free to wrap lines at whitespace characters so as to ensure lines fit within the current window size. Use the &nbsp; entity for the non-breaking space character, when you want to make sure that a line isn't broken! Alternatively, use the NOWRAP attribute to disable word wrapping and the <BR> element to force line breaks where desired.

Netscape includes two tags: <NOBR>...</NOBR>, and <WBR>. The former turns off wordwrapping between the start and end NOBR tag, while WBR is for the rare case when you want to specify where to break the line if needed. Should HTML 3.0 provide an equivalent mechanism to WBR, (either a tag or an entity)?

Permitted AttributesID

An SGML identifier used as the target for hypertext links or for naming particular elements in associated style sheets. Identifiers are NAME tokens and must be unique within the scope of the current document.

LANG

This is one of the ISO standard language abbreviations, e.g. "en.uk" for the variation of English spoken in the United Kingdom. It can be used by parsers to select language specific choices for quotation marks, ligatures and hypenation rules etc. The language attribute is composed from the two letter language code from ISO 639, optionally followed by a period and a two letter country code from ISO 3166.

CLASS

This a space separated list of SGML NAME tokens and is used to subclass tag names. For instance, <H2 CLASS=Section> defines a level 2 header that acts as a section header. By convention, the class names are interpreted hierarchically, with the most general class on the left and the most specific on the right, where classes are separated by a period. The CLASS attribute is most commonly used to attach a different style to some element, but it is recommended that where practical class names should be picked on the basis of the element's semantics, as this will permit other uses, such as restricting search through documents by matching on element class names. The conventions for choosing class names are outside the scope of this specification.

ALIGN Headings are usually rendered flush left. The ALIGN attribute can be used to explicitly specify the horizontal alignment:align=left

The heading is rendered flush left (the default).

align=center

The heading is centered.

align=right

The heading is rendered flush right.

align=justify . 2

Heading lines are justified where practical, otherwise this gives the same effect as the default align=left setting.

For example:

<h1 align=center>This is a centered heading</H1>Here is some text. <H2 align=right>and this is a flush rightheading</H2> Here is some more text.

CLEAR

This attribute is common to all block-like elements. When text flows around a figure or table in the margin, you sometimes want to start an element like a header, paragraph or list below the figure rather than alongside it. The CLEAR attribute allows you to move down unconditionally:

clear=leftmove down until left margin is clear

clear=right

move down until right margin is clear

clear=all

move down until both margins are clear

Alternatively, you can decide to place the element alongside the figure just so long as there is enough room. The minimum width needed is specified as:

clear="40 en" move down until there is at least 40 en units free

clear="100 pixels"

move down until there is at least 100 pixels free

The style sheet (or browser defaults) may provide default minimum widths for each class of block-like elements.

SEQNUM A sequence number is associated with each level of header from the top level (H1) to the bottom level (H6). This attribute is used to set the sequence number associated with the header level of the current element to a given number, e.g. SEQNUM=10. Normally, the sequence number is initialized to 1 at the beginning of the document and incremented after each header element. It is reset to 1 by any header element of a higher level, e.g. an H1 header resets the sequence numbers for H2 to H6. The style of header numbering is controlled by the style sheet.

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SKIP

Increments the sequence number before rendering the element. It is used when headers have been left out of the sequence. For instance, SKIP=3 advances the sequence number past 3 omitted items.

DINGBAT

Specifies an iconic image to appear preceding the header. The icon is specified as an entity name. A list of standard icon entity names for HTML 3.0 is given in an appendix of this specification.

SRC

Specifies an image to appear preceding the header. The image is specified as a URI. This attribute may appear together with the MD attribute.

MD

Specifies a message digest or cryptographic checksum for the associated graphic specified by the SRC attribute. It is used when you want to be sure that a linked object is indeed the same one that the author intended, and hasn't been modified in any way. For instance, MD="md5:jV2OfH+nnXHU8bnkPAad/mSQlTDZ", which specifies an MD5 checksum encoded as a base64 character string. The MD attribute is generally allowed for all elements which support URI based links.

NOWRAP

The NOWRAP attribute is used when you don't want the browser to automatically wrap lines. You can then explicitly specify line breaks in headings using the BR element. For example:

<h1 nowrap>This heading has wordwrap turned off<br>and the BR element is used for explicit line breaks</H1>

html lines Making dividing lines to section off areas of your pages is easy to do. This page gives examples of code above the line created by that code.

basic lines The basic tags, and their modifications, are given below. In each case, the new code is shown in red, and the line beneath it is an example of what that code does.

<hr>

<hr noshade>

line thickness The default line thickness is 2; you can see that in the examples above. Below are some different values for the line thickness.

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<hr size=1>

<hr noshade size=1>

<hr size=3>

<hr noshade size=3>

<hr noshade size=7>

<hr size=7>

line width The "width" tag refers to the left to right size. Default is 100% across the screen, meaning that if you don't specify the width, as in the examples above, the line spans the entire screen. The examples below show the results of specifying the width. On most browsers, the line will be centered.

<hr noshade size=1 width=33>

<hr noshade size=1 width=300>

You can also specify by percent. The percent refers to the percent of the browser screen size; 50% means half the width of the screen, no matter what size it is. The size of the lines below will change if you make your browsers screen wider or narrower; notice, though, that the examples above do not change.

<hr noshade size=1 width="33%">

<hr noshade size=4 width="50%">

<hr size=4 width="50%">

alignment The "align" tag works on most browsers, and will put the line on either the right or left side of the screen.

<hr noshade size=4 width="50%" align=left>

<hr noshade size=4 width="50%" align=right>

<hr size=8 width="50%" align=left>

<hr size=8 width="50%" align=right>

comparing widths - percent vs. numbers Notice the difference between these two examples. In one, the width is given as a number value: 200, which is roughly a third of a full-sized, 15 inch monitor. The second is given as percent: 33%. If you adjust your browser window to make it narrower or wider, you can see that the first example does not change, whereas the second does change.

5<hr size=3 width=200 align=left>

<hr size=3 width="33%" align=left>

color, shape As far as I know, there is no way to specify the color of an HR line. Furthermore, the color of these lines on your screen now depends on the browser, the operating system, and the monitor you're using. On my Macintosh's 256 color screen, using Netscape 3, the unshaded lines are black, and the edges are squared. On my Compaq's million color monitor, using Netscape 3 for Windows 95, the unshaded lines are drab olive or grey, and the edges are rounded if the size is over 5.

However, if you use a background image, and you specify a contrasting background color, the lines will (with certain setups, but not all) take on the color you have specified in the background. (I've seen this work on a Japanese Windows 95 version of Netscape 3 on a 16-bit color Compaq monitor.)

back toHTML Tips Articles Index

Bill Pellowee-mail: billp@gol.com

HTML Paragraphs

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Next Chapter »

HTML documents are divided into paragraphs.

HTML Paragraphs

The HTML <p> element defines a paragraph.

Example<p>This is a paragraph</p><p>This is another paragraph</p>

Try it yourself »

Browsers automatically add an empty line before and after a paragraph.

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HTML Display

You cannot be sure how HTML will be displayed.

Large or small screens, and resized windows will create different results.

With HTML, you cannot change the output by adding extra spaces or extra lines in your HTML code.

The browser will remove extra spaces and extra lines when the page is displayed.

Any number of spaces, and any number of new lines, count as only one space.

Example<p>This paragraphcontains a lot of linesin the source code,but the browser ignores it.</p>

<p>This paragraphcontains a lot of spacesin the source code,but the browser ignores it.</p>

Try it Yourself »

Don't Forget the End Tag

Most browsers will display HTML correctly even if you forget the end tag:

Example<p>This is a paragraph<p>This is another paragraph

Try it yourself »

The example above will work in most browsers, but do not rely on it.

Forgetting the end tag can produce unexpected results or errors.

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Stricter versions of HTML, like XHTML, do not allow you to skip the end tag.

HTML Line Breaks

The HTML <br> element defines a line break.

Use <br> if you want a line break (a new line) without starting a new paragraph:

Example<p>This is<br>a para<br>graph with line breaks</p>

Try it yourself »

The <br> element is an empty HTML element. It has no end tag.

The Poem Problem

Example<p>This poem will display as one line:</p><p> My Bonnie lies over the ocean.

My Bonnie lies over the sea.

My Bonnie lies over the ocean.

Oh, bring back my Bonnie to me.</p>

Try it Yourself »

The HTML <pre> Element

The HTML <pre> element defines preformatted text.

The text inside a <pre> element is displayed in a fixed-width font (usually Courier), and it preserves both spaces and line breaks:

Example<pre> My Bonnie lies over the ocean.

My Bonnie lies over the sea. 8

My Bonnie lies over the ocean.

Oh, bring back my Bonnie to me.</pre>

Try it Yourself »

Test Yourself with Exercises!

Exercise 1 » Exercise 2 » Exercise 3 » Exercise 4 »

HTML Tag Reference

W3Schools' tag reference contains additional information about HTML elements and their attributes.

Tag Description

<p> Defines a paragraph

<br> Inserts a single line break

<pre> Defines pre-formatted text

HTML Comments

Comment is a piece of code which is ignored by any web browser. It is a good practice to add comments into your HTML code, especially in complex documents, to indicate sections of a document, and any other notes to anyone looking at the code. Comments help you and others understand your code and increases code readability.

HTML comments are placed in between <!-- ... --> tags. So any content placed with-in <!-- ... --> tags will be treated as comment and will be completely ignored by the browser.

Example<!DOCTYPE html><html><head> <!-- Document Header Starts --><title>This is document title</title></head> <!-- Document Header Ends --><body><p>Document content goes here.....</p></body></html>

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This will produce following result without displaying the content given as a part of comments:

Document content goes here.....

Valid vs Invalid Comments

Comments do not nest which means a comment can not be put inside another comment. Second the double-dash sequence "--" may not appear inside a comment except as part of the closing --> tag. You must also make sure that there are no spaces in the start-of-comment string.

Example

Here given comment is a valid comment and will be wiped off by the browser.

<!DOCTYPE html><html><head><title>Valid Comment Example</title></head><body><!-- This is valid comment --><p>Document content goes here.....</p></body></html>

But following line is not a valid comment and will be displayed by the browser. This is because there is a space between the left angle bracket and the exclamation mark.

<!DOCTYPE html><html><head> <title>Invalid Comment Example</title></head> <body>< !-- This is not a valid comment --><p>Document content goes here.....</p></body></html>This will produce following result:< !-- This is not a valid comment --> Document content goes here.....

Multiline CommentsSo far we have seen single line comments, but HTML supports multi-line comments as well.

You can comment multiple lines by the special beginning tag <!-- and ending tag --> placed before the first line and end of the last line as shown in the given example below.

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Example<!DOCTYPE html><html><head> <title>Multiline Comments</title></head> <body><!-- This is a multiline comment and it canspan through as many as lines you like.--><p>Document content goes here.....</p></body></html>

This will produce following result:

Document content goes here.....Conditional CommentsConditional comments only work in Internet Explorer (IE) on Windows but they are ignored by other browsers. They are supported from Explorer 5 onwards, and you can use them to give conditional instructions to different versions of IE.

Example<!DOCTYPE html><html><head> <title>Conditional Comments</title>

<!--[if IE 6]> Special instructions for IE 6 here<![endif]--></head> <body><p>Document content goes here.....</p></body></html>

You will come across a situation where you will need to apply a different style sheet based on different versions of Internet Explorer, in such situation conditional comments will be helpful.

Using Comment Tag

There are few browsers that support <comment> tag to comment a part of HTML codeExample<!DOCTYPE html><html><head><title>Using Comment Tag</title>

</head><body><p>This is <comment>not</comment> Internet Explorer.</p></body></html>

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If you are using IE then it will produce following result:This is Internet Explorer.But if you are not using IE, then it will produce following result:This is Internet Explorer.

Commenting Script Code

Though you will learn Javascript with HTML, in a separate tutorial, but here you must make a note that if you are using Java Script or VB Script in your HTML code then it is recommended to put that script code inside proper HTML comments so that old browsers can work properly.

Example<!DOCTYPE html><html><head><title>Commenting Script Code</title><script><!-- document.write("Hello World!")//--></script></head><body><p>Hello , World!</p></body></html>

This will produce following result:

Hello World!

Hello , World!

Commenting Style Sheets

Though you will learn using style sheets with HTML in a separate tutorial, but here you must make a note that if you are using Casecading Style Sheet (CSS) in your HTML code then it is recommended to put that style sheet code inside proper HTML comments so that old browsers can work properly.

Example<!DOCTYPE html><html><head><title>Commenting Style Sheets</title><style><!--.example { border:1px solid #4a7d49;

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HTML Element Reference

Tag Description<!--...--> Defines a comment<!DOCTYPE>  Defines the document type<a> Defines a hyperlink<abbr> Defines an abbreviation or an acronym

<acronym>Not supported in HTML5. Use <abbr> instead.Defines an acronym

<address> Defines contact information for the author/owner of a document

<applet>Not supported in HTML5. Use <embed> or <object> instead.Defines an embedded applet

<area> Defines an area inside an image-map<article> Defines an article<aside> Defines content aside from the page content<audio> Defines sound content<b> Defines bold text<base> Specifies the base URL/target for all relative URLs in a document

<basefont>Not supported in HTML5. Use CSS instead.Specifies a default color, size, and font for all text in a document

<bdi>Isolates a part of text that might be formatted in a different direction from other text outside it

<bdo> Overrides the current text direction

<big>Not supported in HTML5. Use CSS instead.Defines big text

<blockquote> Defines a section that is quoted from another source<body> Defines the document's body<br> Defines a single line break<button> Defines a clickable button<canvas> Used to draw graphics, on the fly, via scripting (usually JavaScript)<caption> Defines a table caption

<center>Not supported in HTML5. Use CSS instead.Defines centered text

<cite> Defines the title of a work<code> Defines a piece of computer code

<col>Specifies column properties for each column within a <colgroup> element 

<colgroup> Specifies a group of one or more columns in a table for formatting<datalist> Specifies a list of pre-defined options for input controls<dd> Defines a description/value of a term in a description list<del> Defines text that has been deleted from a document<details> Defines additional details that the user can view or hide<dfn> Represents the defining instance of a term

<dialog> Defines a dialog box or window

<dir>Not supported in HTML5. Use <ul> instead.Defines a directory list

<div> Defines a section in a document<dl> Defines a description list<dt> Defines a term/name in a description list<em> Defines emphasized text <embed> Defines a container for an external (non-HTML) application<fieldset> Groups related elements in a form<figcaption> Defines a caption for a <figure> element<figure> Specifies self-contained content

<font>Not supported in HTML5. Use CSS instead.Defines font, color, and size for text

<footer> Defines a footer for a document or section<form> Defines an HTML form for user input

<frame>Not supported in HTML5.Defines a window (a frame) in a frameset

<frameset>Not supported in HTML5.Defines a set of frames

<h1> to <h6> Defines HTML headings<head> Defines information about the document<header> Defines a header for a document or section<hr> Defines a thematic change in the content<html> Defines the root of an HTML document<i> Defines a part of text in an alternate voice or mood<iframe> Defines an inline frame<img> Defines an image<input> Defines an input control<ins> Defines a text that has been inserted into a document<kbd> Defines keyboard input<keygen> Defines a key-pair generator field (for forms)<label> Defines a label for an <input> element<legend> Defines a caption for a <fieldset> element<li> Defines a list item

<link>Defines the relationship between a document and an external resource (most used to link to style sheets)

<main> Specifies the main content of a document<map> Defines a client-side image-map<mark> Defines marked/highlighted text<menu> Defines a list/menu of commands

<menuitem>Defines a command/menu item that the user can invoke from a popup menu

<meta> Defines metadata about an HTML document<meter> Defines a scalar measurement within a known range (a gauge)<nav> Defines navigation links

<noframes>Not supported in HTML5.Defines an alternate content for users that do not support frames

<noscript>Defines an alternate content for users that do not support client-side scripts

<object> Defines an embedded object<ol> Defines an ordered list<optgroup> Defines a group of related options in a drop-down list<option> Defines an option in a drop-down list<output> Defines the result of a calculation<p> Defines a paragraph<param> Defines a parameter for an object<pre> Defines preformatted text<progress> Represents the progress of a task<q> Defines a short quotation<rp> Defines what to show in browsers that do not support ruby annotations

<rt>Defines an explanation/pronunciation of characters (for East Asian typography)

<ruby> Defines a ruby annotation (for East Asian typography)<s> Defines text that is no longer correct<samp> Defines sample output from a computer program<script> Defines a client-side script<section> Defines a section in a document<select> Defines a drop-down list<small> Defines smaller text

<source>Defines multiple media resources for media elements (<video> and <audio>)

<span> Defines a section in a document

<strike>Not supported in HTML5. Use <del> or <s> instead.Defines strikethrough text

<strong> Defines important text<style> Defines style information for a document<sub> Defines subscripted text<summary> Defines a visible heading for a <details> element<sup> Defines superscripted text<table> Defines a table<tbody> Groups the body content in a table<td> Defines a cell in a table<textarea> Defines a multiline input control (text area)<tfoot> Groups the footer content in a table

<th> Defines a header cell in a table<thead> Groups the header content in a table<time> Defines a date/time<title> Defines a title for the document<tr> Defines a row in a table<track> Defines text tracks for media elements (<video> and <audio>)

<tt>Not supported in HTML5. Use CSS instead.Defines teletype text

<u> Defines text that should be stylistically different from normal text<ul> Defines an unordered list<var> Defines a variable<video> Defines a video or movie<wbr> Defines a possible line-break