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The HyperText Markup Language (HTML) is composed of a set of elements
that define a document and guide its display.
This document presents a concise reference guide to HTML,
listing the most commonly used elements from Versions 1 and 2 of HTML,
and giving a brief description of those elements.


Users should be aware that HTML is an evolving language, and
different World-Wide Web browsers may recognize slightly different sets of
HTML elements.
For general information about HTML including plans for new versions, see

http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html.
For a comprehensive list of HTML elements see

http://www.sandia.gov/sci_compute/html_ref.html


This document is available in two formats:




Introduction



An HTML element may include a name, some attributes and some
text or hypertext, and will appear in an HTML document as


<tag_name> text </tag_name>
<tag_name attribute_name=argument>
text </tag_name>, or just
<tag_name>


For example:


<title> My Useful Document </title>


and


<a href="argument"> text </a>


An HTML document is composed of a single element:


<html> . . . </html>


that is, in turn, composed of head and body elements:


<head> . . . </head>


and


<body> . . . </body>


To allow older HTML documents to remain readable, <html>,
<head>, and <body> are actually
optional within HTML documents.

Elements usually placed in the head element





<isindex>
Specifies that the current
document describes a database that can be searched using the index
search method appropriate for whatever client is being used to read
the document. For example, a Lynx user will use the "s" keyboard
command.

<title> . . . </title>
Specify a document title. Note that the title will not appear on the
document as is customary on printed documents. It will usually appear
in a window bar identifying the contents of the window.
HTML header tags perform the functions usually reserved for titles.

<base href="URL">
Specify the
name of the file relative to which partially qualified pathnames
in URLs should be interpreted. If not otherwise specified the URL
containing the document being displayed is used as the base.

<link rev="RELATIONSHIP" rel="RELATIONSHIP" href="URL">
The link tag allows you to define relationships between the
document containing the link tag and the document specified in
the "URL".
The rel attribute specifies the
relationship between the HTML file and the Uniform Resource
Locator (URL).
The rev attribute (for "reverse")
specifies the relationship between the URL and the HTML file.
For example, <link rev="made" href="URL">
indicates that the file maker or owner is
described in the document identified by the URL.
(Note that link tags are not displayed on the screen as part of
the document. They define static relationships, not hypertext links.)



Elements usually placed in the body element


The following sections describe elements that can be used
in the body of the document.



Text Elements



<p>
The end of a paragraph that will be formatted
before it is displayed on the screen.

<pre> . . . </pre>
Identifies text that has already been formatted (preformatted) by some other
system and must be displayed as is. Preformatted text may include
embedded tags, but not all tag types are permitted.
The <pre> tag can be used to include tables in
documents.

<listing> . . . </listing>
Example computer listing; embedded tags will be ignored, but embedded tabs
will work. This is an archaic tag.

<xmp> . . . </xmp>
Similar to <pre> except no embedded tags will
be recognized.

<plaintext>
Similar to <pre> except no embedded tags will
be recognized, and since there is no end tag, the remainder of the
document will be rendered as plain text. This is an archaic tag.
Note that some browsers actually recognize a </plaintext>
tag, even though it is not defined by the standard.

<blockquote> . . . </blockquote>
Include a section of text quoted from some other source.



Hyperlinks or Anchors



<a name="anchor_name"> . . .
</a>
Define a target location in a document

<a href="#anchor_name"> . . .
</a>
Link to a location in the base document, which
is the document containing the anchor tag itself, unless a base
tag has been specified.

<a href="URL"> . . .
</a>
Link to another file or resource

<a href="URL#anchor_name"> . . .
</a>
Link to a target location in another document

<a href="URL?search_word+search_word"> . . .
</a>
Send a search string to a server.
Different servers may interpret the search string differently.
In the case of word-oriented search engines, multiple search words
might be specified by separating individual
words with a plus sign (+).



An anchor must include a name or href attribute,
and may include both. There are several optional attributes, but they
are rarely encountered.


The structure of a Uniform Resource Locator (URL) may be expressed as:



resource_type:additional_information



where the possible resource types include: file,
http, news, gopher,
telnet, ftp,
and wais, among others, and each resource type relates to
a specific server type. Since each server performs a unique function,
each resource type requires different additional_information.
For example http and gopher URLs will
have a structure like:



resource_type://host.domain:port/pathname


The colon followed by an integer TCP port
number is optional, and is used when a server is listening on a
non-standard port.


Strictly speaking, the anchor_name
and search_word information included
in the name and
href attributes in the examples above are part of the URL.
They are presented as separate entities for simplicity.
A more complete description of URLs is presented
in
http://www.w3.org/hypertext/WWW/Addressing/Addressing.html

Headers



<h1> . . .
</h1> Most prominent header

<h2> . . .
</h2>

<h3> . . .
</h3>

<h4> . . .
</h4>

<h5> . . .
</h5>

<h6> . . .
</h6> Least prominent header



Logical Styles



<em> . . .
</em>
Emphasis

<strong> . . .
</strong>
Stronger emphasis

<code> . . .
</code>
Display an HTML directive

<samp> . . .
</samp>
Include sample output

<kbd> . . .
</kbd>
Display a keyboard key

<var> . . .
</var>
Define a variable

<dfn> . . .
</dfn>
Display a definition (not widely supported)

<cite> . . .
</cite>
Display a citation



Physical Styles




<b> . . . </b>
Boldface

<i> . . . </i>
Italics

<u> . . . </u>
Underline

<tt> . . . </tt>
Typewriter font



Definition list/glossary: <dl>



<dl>

<dt> First term to be defined

<dd> Definition of first term

<dt> Next term to be defined

<dd> Next definition

</dl>


The <dl> attribute compact can be used to
generate a definition list requiring less space.



Present an unordered list: <ul>



<ul>

<li> First item in the list

<li> Next item in the list

</ul>



Present an ordered list: <ol>



<ol>

<li> First item in the list

<li> Next item in the list

</ol>



Present an interactive menu: <menu>



<menu>

<li> First item in the menu

<li> Next item

</menu>



Present a directory list of items: <dir>



<dir>

<li> First item in the list

<li> Second item in the list

<li> Next item in the list

</dir>



Items should be less than 20 characters long.



Entities




&keyword;
Display a particular character identified by a special
keyword. For example the entity &amp; specifies the
ampersand ( & ),
and the entity &lt; specifies the less than
( < ) character.
Note that the semicolon
following the keyword is required, and the keyword must be one from the
lists presented in:

http://www.w3.org/pub/WWW/MarkUp/html-spec/html-spec_9.html#SEC9.7

&#ascii_equivalent;
Use a character literally. Again note
that the semicolon following the ASCII numeric value is required.



HTML Forms Interface


The HTML forms interface allows document creators to define HTML
documents containing forms to be filled out by users.
When a user fills out the form and presses a button indicating the
form should be "submitted," the information on the form is sent to
a server for processing. The server will usually prepare an HTML
document using the information supplied by the user and return it to
the client for display.


The following tags implement the forms interface:



The last four tags can only be used within a
<form> . . . </form> element.

Define a form


<form> . . . </form>


Defines a form within an HTML document.
A document may contain multiple <form> elements, but
<form> elements may not be nested.
Note that non-form tags can be used within a <form> element.
Attributes and their arguments:


action="URL":
The location of the program that will process the form.
method=data_exchange method
The method chosen to exchange data between the client and the program
started to process the form:
One of get or post.
post is preferred for most applications.



Example:
<form action="http://www.cc.ukans.edu/cgi-bin/register" method=post> . . . </form>



Define an input field



<input> (there is no ending tag)


Defines an input field where the user may enter information on the form.
Each input field assigns a value to a variable which has a specified
name and a specified data type.
Attributes and their arguments:


type="variable_type"
Specifies the data type for the variable, where:


name="textstring"
where textstring is a symbolic
name (not displayed) identifying the input variable as in:


<input type="checkbox" name="box1">

value="textstring"
where the meaning of textstring
depends on the argument for type.




checked
No arguments. For type="checkbox"
or type="radio",
if checked is present the input field
is "checked" by default.

size="display_width"
where display_width is an integer value
representing the number of
characters displayed for the type="text"
or type="password" input field.

maxlength="string_length"
where string_length is the maximum number of characters
allowed within type="text" or type="password"
variable values.
This attribute is only valid for single line "text"
or "password" fields.


Define a select field


<select> . . . </select>


Defines and displays a set of optional list items from which the user
can select one or more items.
This element requires an <option> element for each
item in the list.
Attributes and their arguments:


name="textstring"
where textstring is the
symbolic identifier for the select field variable.

size="list_length"
where list_length is an integer value representing
the number of <option> items that will be
displayed at one time.

multiple
No arguments. If present, the multiple attribute
allows selection of more than one <option> value.



Define a select field option


<option>


Within the <select> element the <option>
tags are used to define the possible values for the select
field. If the attribute selected is present then the
option value is selected by default. In the following example
all three options may be chosen but bananas are selected by default.


<select multiple>

<option>Apples

<option selected>Bananas

<option>Cherries

</select>


Define a text area


<textarea> . . . default text . . . </textarea>


Defines a rectangular field where the user may enter text data.
If "default text" is present it will be displayed when the field
appears. Otherwise the field will be blank.
Attributes and their values:


name="textstring"
textstring is a symbolic
name that identifies the <textarea> variable.

rows="num_rows" and cols="numcols"
Both attributes take an integer value which represents the
lines and number of characters per line in the <textarea>
to be displayed.




Miscellaneous




<!-- text -->
Place a comment in the HTML source

<address> . . .
</address>
Present address information

<img src="URL" alt="Alternate Text">
Embed a
graphic image in the document. Attributes:


src
Specifies the location of the image.
alt
Allows a text string to be put in place of the image
in clients that cannot display images.
align
Specify a relationship to surrounding text.
The argument for align can be one of top,
middle, or bottom.
ismap
If ismap is present and the image tag is within
an anchor, the image will become a "clickable image". The pixel
coordinates of the cursor will be appended to the URL specified in the
anchor if the user clicks within the ismap image. The resulting URL will
take the form "URL?m,n" where m and n are integer coordinates, and the
URL will specify the location of a program that will examine
the pixel coordinates, and return an appropriate document.



<br>
Forces a line break immediately and retains
the same style.

<hr>

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