COL - Table Column

<COL>

ALIGN=[ left | center | right | justify | char ] (horizontal alignment of cells)
VALIGN=[ top | middle | bottom | baseline ] (vertical alignment of cells)
SPAN=Number (number of columns)
WIDTH=MultiLength (width of each column)
CHAR=Character (alignment character for cells)
CHAROFF=Length (alignment character offset)
ID=string
CLASS=string
STYLE=string
TITLE=string
LANG=Language (i.e. RU - Russian)
DIR=ltr|rtl
SCRIPTING EVENTS=string

Empty

COLGROUP, TABLE

The COL element defines attributes common to a table column. If used, COL must be after the optional CAPTION and before the optional THEAD in the TABLE. Unlike COLGROUP, COL does not group columns structurally; it merely defines attributes common to all cells in one or more columns.

COL also takes a number of presentational attributes, many of which cannot be completely replaced by style sheets. Since few browsers support COL, authors may wish to specify these attributes on the TD or TH elements instead.

COL's SPAN attribute defines the number of columns that will share the COL element's other attributes; the default value is 1. COL may be contained directly in the TABLE element or it may be contained within a COLGROUP. If COL is in a COLGROUP, the COL's attributes override those of the COLGROUP for the columns spanned by COL.

The next example uses COL elements within COLGROUPs to assign a different CLASS to each column:

<TABLE SUMMARY="This table gives the character entity reference,
                decimal character reference, and hexadecimal character
                reference for 8-bit Latin-1 characters, as well as the
                rendering of each in your browser.">
  <COLGROUP CLASS="character-description">
  <COLGROUP>
    <COL CLASS=entity>
    <COL SPAN=2 CLASS=numeric>
  <COLGROUP>
    <COL CLASS="entity-rendering">
    <COL CLASS="decimal-rendering">
    <COL CLASS="hex-rendering">
  <THEAD>
    <TR>
      <TH SCOPE=col ROWSPAN=2>Character</TH>
      <TH SCOPE=col ROWSPAN=2>Entity</TH>
      <TH SCOPE=col ROWSPAN=2>Decimal</TH>
      <TH SCOPE=col ROWSPAN=2>Hex</TH>
      <TH SCOPE=colgroup COLSPAN=3>Rendering in Your Browser</TH>
    </TR>
    <TR>
      <TH SCOPE=col>Entity</TH>
      <TH SCOPE=col>Decimal</TH>
      <TH SCOPE=col>Hex</TH>
    </TR>
  </THEAD>
  <TBODY>
    <TR>
      <TD SCOPE=row>non-breaking space</TD>
      <TD>&amp;nbsp;</TD>
      <TD>&amp;#160;</TD>
      <TD>&amp;#xA0;</TD>
      <TD>&nbsp;</TD>
      <TD>&#160;</TD>
      <TD>&#xA0;</TD>
    </TR>
    ...
  </TBODY>
</TABLE>

The WIDTH attribute specifies a width for each column spanned by COL. The value must be a number in pixels, a percentage of the table width, or a relative length expressed as i* where i is an integer. A column with WIDTH="3*" will be allotted three times the width of a column with WIDTH="1*". The value 0* is equivalent to the minimum width necessary for the column's contents.

The ALIGN attribute specifies the horizontal alignment for each cell in the spanned columns. Possible values are left, center, right, justify, and char. ALIGN=char aligns a cell's contents on the character given in the CHAR attribute. The default value for the CHAR attribute is the decimal point of the current language--a period in English. The CHAROFF attribute specifies the offset to the first occurrence of the alignment character. The attribute's value is a number in pixels or a percentage of the cell's width; CHAROFF="50%" centers the alignment character horizontally in a cell.

The VALIGN attribute specifies the vertical position of a cell's contents. Possible values are:

• top, which positions data at the top of the cell;
• middle, the default value, which centers the cell data vertically;
• bottom, which positions data at the bottom of the cell;
• baseline, which specifies that the first line of each cell in the row with ALIGN=baseline should occur on a common baseline.

The ID attribute uniquely identifies an element within a document. No two elements can have the same ID value in a single document. The attribute's value must begin with a letter in the range A-Z or a-z and may be followed by letters (A-Za-z), digits (0-9), hyphens ("-"), underscores ("_"), colons (":"), and periods (".").

The following example uses the ID attribute to identify each of the first two paragraphs of a document:

<P ID=firstp>My first paragraph.</P>
<P ID=secondp>My second paragaph.</P>

The paragraphs in the example could have style rules associated with them through their ID attributes. The following Cascading Style Sheet defines unique colors for the two paragraphs:

P#firstp {
  color: navy;
  background: transparent
}

P#secondp {
  color: black;
  background: transparent
}

The paragraphs in the initial example could also be used as a target anchor for links:

<P>See <A HREF="#firstp">the opening paragraph</A> for more information.</P>

The CLASS attribute specifies the element to be a member of one or more classes. Classes allow authors to define specific kinds of a given element. For example, an author could use <CODE CLASS=Java> when giving Java code and <CODE CLASS=Perl> when giving Perl code.

Unlike with the ID attribute, any number of elements can share the same class. An element may also belong to multiple classes; the CLASS attribute value is a space-separated list of class names.

Note that most current browsers do not support multiple classes. Such browsers typically ignore a CLASS attribute that specifies multiple classes.

The CLASS attribute is particularly useful when combined with style sheets. For example, consider the following navigation bar:

<DIV CLASS=navbar>
<P><A HREF="/">Home</A> | <A HREF="./">Index</A> | <A HREF="/search.html">Search</A></P>
<P><A HREF="/"><IMG SRC="logo.gif" ALT="" TITLE="WDG Logo"></A></P>
</DIV>

This example's use of the CLASS attribute allows style rules to easily be added. The following Cascading Style Sheet suggests a presentation for the preceding example:

.navbar {
  margin-top: 2em;
  padding-top: 1em;
  border-top: solid thin navy
}

.navbar IMG { float: right }

@media print {
  .navbar { display: none }
}

The STYLE attribute allows authors to specify style rules inline for a single occurrence of an element. An example follows:

<P>A popular font for on-screen reading is <SPAN STYLE="font-family: Verdana">Verdana</SPAN>.</P>

When the STYLE attribute is used, a default style sheet language must be specified for the document by setting the Content-Style-Type HTTP header to the media type of the style sheet language. The previous example could use the following META element in the document's HEAD:

<META HTTP-EQUIV="Content-Style-Type" CONTENT="text/css">

In most cases, use of the CLASS or ID attributes is a better choice than using STYLE since ID and CLASS can be selectively applied to different media and since they provide a separation of content and presentation that often simplifies maintenance.

The TITLE attribute provides a title for an element and is commonly implemented as a "tooltip" on visual browsers, though many browsers lack support for TITLE. The attribute is most useful with A, LINK, IMG, and OBJECT elements, where it provides a title for the linked or embedded resource. Some examples follow:

• <A HREF="mailto:liam@htmlhelp.com" TITLE="Feedback on HTML 4.0 Reference">liam@htmlhelp.com</A>
• <A HREF="http://www-genome.wi.mit.edu/ftp/pub/software/WWW/cgi_docs.html" TITLE="CGI.pm - a Perl5 CGI Library">CGI.pm</A>
• <LINK REL=Alternate HREF="index.fr.html" HREFLANG=fr LANG=fr TITLE="Version française">
• <OBJECT CLASSID="java:Yahtzee.class" CODETYPE="application/java" WIDTH=400 HEIGHT=250 STANDBY="Ready to play Yahtzee?" TITLE="My Yahtzee Game">
<IMG SRC="yahtzee.gif" ALT="" TITLE="A Yahtzee animation">
Yahtzee is my <EM>favorite</EM> game!
</OBJECT>

TITLE is also helpful with the ABBR and ACRONYM elements to provide the long form of the abbreviation. Examples:

• He weighs 180 <ABBR TITLE=pounds>lbs.</ABBR>
• <ABBR TITLE="Parti Québécois" LANG=fr-CA>PQ</ABBR>
• <ACRONYM TITLE="North Atlantic Treaty Organization">NATO</ACRONYM>

The LANG attribute specifies the language of an element's attribute values and its content, including all contained elements that do not specify their own LANG attribute. While the LANG attribute is not widely supported, its use may help search engines index a document by its language while allowing speech synthesizers to use language-dependent pronunciation rules. As well, visual browsers can use the language's proper quotation marks when rendering the Q element.

The attribute value is case-insensitive, and should be specified according to RFC 1766; examples include en for English, en-US for American English, and ja for Japanese. Whitespace is not allowed in the language code.

Use of the LANG attribute also allows authors to easily change the style of text depending on the language. For example, a bilingual document may have one language in italics if rendered visually or a different voice if rendered aurally. The HTML of such a document might be as follows:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"
   "http://www.w3.org/TR/REC-html40/strict.dtd">
<TITLE>Welcome - Bienvenue</TITLE>
<H1>
  <SPAN LANG=en>Welcome</SPAN> -
  <SPAN LANG=fr>Bienvenue</SPAN>
</H1>
<P LANG=en>This paragraph is in English.</P>
<P LANG=fr>Ce paragraphe est en français.</P>
...

A document's primary language may be set using the LANG attribute on the HTML element, or, alternatively, by using the Content-Language HTTP header.

A number of attributes that define client-side scripting events are common to most elements. The attribute value is a script--typically a function call or a few short statements--that is executed when the event occurs. The value may contain entities (e.g., &quot;).

The following example features JavaScript code to handle two events of a submit button, giving the user a reminder in the status bar when the mouse moves over the button and clearing the status bar when the mouse moves away. Note that the attribute values are delimited by single quotes since double quotes are used within them.

<INPUT TYPE=submit ONMOUSEOVER='window.status="Did you fill in all required fields?";' ONMOUSEOUT='window.status="";'>

When an event attribute is used, a default scripting language must be specified for the document by setting the Content-Script-Type HTTP header to the media type of the scripting language. The previous example could use the following META element in the document's HEAD:

<META HTTP-EQUIV="Content-Script-Type" CONTENT="text/javascript">

The common event attributes are device-dependent and largely tailored for the graphical user interface. The available events are as follows:

• ONCLICK, when the mouse button is clicked on an element;
• ONDBLCLICK, when the mouse button is double-clicked on an element;
• ONMOUSEDOWN, when the mouse button is pressed over an element;
• ONMOUSEUP, when the mouse button is released over an element;
• ONMOUSEOVER, when the mouse is moved onto an element;
• ONMOUSEMOVE, when the mouse is moved while over an element;
• ONMOUSEOUT, when the mouse is moved away from an element;
• ONKEYPRESS, when a key is pressed and released over an element;
• ONKEYDOWN, when a key is pressed down over an element;
• ONKEYUP, when a key is released over an element.