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
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>
<title> My Useful Document </title>
<a href="argument"> text </a>
<html>
. . .
</html>
<head>
. . .
</head>
<body>
. . .
</body>
<html>
,
<head>
, and
<body>
are actually optional within HTML documents.
<isindex>
<title>
. . .
</title>
<base href="URL">
<link rev="RELATIONSHIP" rel="RELATIONSHIP" href="URL">
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.)
<p>
<pre>
. . .
</pre>
<pre>
tag can be used to include tables in documents.
<listing>
. . .
</listing>
<xmp>
. . .
</xmp>
<pre>
except no embedded tags will be recognized.
<plaintext>
<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>
<a name="anchor_name">
. . .
</a>
<a href="#anchor_name">
. . .
</a>
<a href="URL">
. . .
</a>
<a href="URL#anchor_name">
. . .
</a>
<a href="URL?search_word+search_word">
. . .
</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:
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:
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
<h1>
. . .
</h1>
Most prominent header
<h2>
. . .
</h2>
<h3>
. . .
</h3>
<h4>
. . .
</h4>
<h5>
. . .
</h5>
<h6>
. . .
</h6>
Least prominent header <em>
. . .
</em>
<strong>
. . .
</strong>
<code>
. . .
</code>
<samp>
. . .
</samp>
<kbd>
. . .
</kbd>
<var>
. . .
</var>
<dfn>
. . .
</dfn>
<cite>
. . .
</cite>
<b>
. . .
</b>
<i>
. . .
</i>
<u>
. . .
</u>
<tt>
. . .
</tt>
<dl>
<dt>
First term to be defined
<dd>
Definition of first term
<dt>
Next term to be defined
<dd>
Next definition
</dl>
<dl>
attribute
compact
can be used to generate a definition list requiring
less space.
<ul>
<li>
First item in the list
<li>
Next item in the list
</ul>
<ol>
<li>
First item in the list
<li>
Next item in the list
</ol>
<menu>
<li>
First item in the menu
<li>
Next item
</menu>
<dir>
<li>
First item in the list
<li>
Second item in the list
<li>
Next item in the list
</dir>
&
keyword
;
&
specifies the ampersand ( & ), and the entity
<
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:
&#
ascii_equivalent
;
The following tags implement the forms interface:
<form>
. . .
</form>
<input>
<select>
. . .
</select>
<option>
<textarea>
. . .
</textarea>
<form>
. . .
</form>
element.
<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="URL"
:
method=data_exchange method
get
or
post
.
post
is preferred for most applications. <form action="http://kuhttp.cc.ukans.edu/cgi-bin/register"
method=post>
. . .
</form>
<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"
type="text"
and
type="password"
fields accept character data
type="checkbox"
fields are either selected or not
type="radio"
fields of the same name allow selection of only
one of the associated values
type="submit"
defines an action button that sends the completed
form to the query server
type="reset"
defines a button that resets the form variables to
their default values
type="hidden"
defines an invisible input field whose value will
be sent along with the other form values when the form is submitted. This is
used to pass state information from one script or form to another. name="textstring"
textstring
is a symbolic name (not displayed) identifying the
input
variable as in:
<input type="checkbox" name="box1">
value="textstring"
textstring
depends on the argument for
type
.
type="text"
or
type="password"
,
textstring
is the default value for the
input
variable. Password values will not be shown on the user's
form. Anything entered by the user will replace any default value defined
with this attribute.
type="checkbox"
or
type="radio"
,
textstring
is the value that will be sent to the server if the
checkbox is "checked".
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
type="checkbox"
or
type="radio"
, if
checked
is present the
input
field is "checked" by default.
size="display_width"
display_width
is an integer value representing the number of
characters displayed for the
type="text"
or
type="password" input
field.
maxlength="string_length"
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. <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"
textstring
is the symbolic identifier for the
select
field variable.
size="list_length"
list_length
is an integer value representing the number of
<option>
items that will be displayed at one time.
multiple
multiple
attribute allows selection of more than one
<option>
value. <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>
<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"
<textarea>
to be displayed. <!--
text
-->
<address>
. . .
</address>
<img src="URL" alt="Alternate Text">
src
alt
align
align
can be one of
top
,
middle
, or
bottom
.
ismap
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>
<hr>
For an introduction to forms within HTML see: An Instantaneous Introduction to CGI Scripts and HTML Forms.
For general information about HTML, see http://www.w3.org/hypertext/WWW/MarkUp/MarkUp.html
Michael Grobe