HTML Quick Reference

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 Level 1 of HTML, listing almost all of the Level 1 elements, 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.

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 in which the current document is stored. This is useful when link references within the document do not include full pathnames (i.e., are partially qualified).
<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 same document
<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://host.domain:port/pathname

where the possible resource types include: file, http, news, gopher, telnet, ftp, and wais, among others, and each resource type interprets the pathname in its own way. (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.) Note that each resource type relates to a specific server type. The colon followed by an integer TCP port number is optional, and is used when a server is listening on a non-standard port.

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 & specifies the ampersand ( & ), and the entity < specifies the less than ( < ) character.
&#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:

<form> . . . </form>
<input>
<select> . . . </select>
<option>
<textarea> . . . </textarea>

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

Define a form

<form> . . . </form>

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

Example:
: <form action="http://kuhttp.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

Specifies the data type for the variable.

type="text" and type="password" accept character data
type="checkbox" is either selected or not
type="radio" allows selection of only one of several radio fields, if they all have the same variable name
type="submit" is an action button that sends the completed form to the query server
type="reset" is a button that resets the form variables to their default values

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 function of textstring depends on the argument for type.

For type="text" or type="password", textstring is the default value for the input variable.
If type="checkbox" or type="radio", textstring is the value of the input variable when it is "checked".
For type="reset" or type="submit", textstring is a label that will appear on the submit or reset button in place of the words "submit" and "reset".

checked

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

size

width where width is an integer value representing the number of characters allowed for the type="text" or type="password" input fields.

maxlength

length where length is the number of characters accepted for type="text" or type="password". 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: The argument for size 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" where textstring is a symbolic name that identifies the <textarea> variable.
rows and cols: Both attributes take an integer value which represents the lines and number of characters per line in the <textarea> to be displayed.

Miscellaneous

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.

<br>

Forces a line break immediately and retains the same style.

<hr>

Places a horizontal rule or separator between sections of text.

Additional Information

For a tutorial introduction to HTML see: html-primer.html.

Michael Grobe
Academic Computing Services
The University of Kansas
grobe@kuhub.cc.ukans.edu
February 14, 1995