A Href

Hyperlink [A Href] Support Key: [2\|3\|3.2\|4] [X1\|X1.1] [IE1\|M1\|N1\|O2.1]	What is it? Attributes Tag Example	Parent/Content Model Tips & Tricks Browser Peculiarities
= Index DOT Html by Brian Wilson =

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Quick Statistics
End Tag:		Required
Standards Details:		In all HTML 4.x/XHTML DTDs
XHTML Modules:		Hypertext
CSS 'display' Type:		"inline"
CSS Mapping:		a:link, a:visited, a:active
Default Rendering:		Underlined content - usually blue for unvisited content, purple for visited.
Official Docs:		HTML 4.x, XHTML 1.1

What is it?: The A element is one of the key distinctive features of HTML. It defines a link between resources that allows webs of information to be created. The Hyperlink element indicates a portion of text and/or an object that serves as a hot area for the user to activate to jump to another location. The A element can serve as a destination of a URL, an invocation of a URL, or both at the same time.

To invoke a Bookmark either in a current document or in a remote document, the Bookmark NAME must be prefaced by a hash mark symbol ("#") [See examples below.] If no Bookmark is specified in the HREF statement, the browser will default to the top of the document.

Common Attributes

%Core%

[2|3|3.2|4] [X1|X1.1] [IE3|M|N4B3|O3.5]

%Accessibility%

[2|3|3.2|4] [X1|X1.1] [IE4B1|M|N6|O3]

%Events%

[2|3|3.2|4] [X1|X1.1] [IE3|M|N2|O3]

%Language%

[2|3|3.2|4] [X1|X1.1] [IE4|M|N|O]

%Data%

[2|3|3.2|4] [X1|X1.1] [IE4|M|N|O]

%Editing%

[2|3|3.2|4] [X1|X1.1] [IE5.5|M|N|O]

Specific Attributes

Accesskey

[2|3|3.2|4] [X1|X1.1] [IE4B1|M|N6B2|O7]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This is a method of giving access/focus to an active HTML element using a keyboard character. This is a common GUI paradigm also known as a "keyboard shortcut" or "keyboard accelerator" A single character is used as the value of this attribute. In addition, a platform-dependent key is usually used in combination with the ACCESSKEY character to access the functionality of the active field.

Values: CDATA. [A single, case-insensitive character from a browser's character set.]

Charset

[2|3|3.2|4] [X1|X1.1] [IE|M|N|O7]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This attribute indicates the character encoding of the destination resource of the hyperlink.

Values: CDATA. [A recognized RFC 2045 language character set string. Default is ISO-8859-1.]

Coords

[2|3|3.2|4] [X1|X1.1] [IE|M|N6|O7]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This specifies the coordinate values in pixels appropriate to the accompanying SHAPE attribute to define a region of an image for hyperlinking. The coordinate system for Client Side Image Maps originates at the top, left corner of the image and values grow larger as you move down and to the right.
These are the corresponding SHAPE types and COORDS definition schemes:
   RECT, RECTANGLE: COORDS="left,top,right,bottom"
   CIRC, CIRCLE:            COORDS="center_x,center_y,radius"
   POLY, POLYGON:       COORDS="x1,y1,x2,y2,...,xn,yn"
[The Polygon values specify the successive coordinates of the polygon and have no explicit limit on number of vertices, but HTML limits attribute values to 1024 characters. If the first and last coordinates of a Polygon reference are not the same, then a final segment is implied to close it.]

Values: CDATA. [Positive integers given as a comma separated list of X-Y values.]

Disabled

[2|3|3.2|4] [X1|X1.1] [IE5|M|N|O7]

Standards Details: NA

Required? No

Description:
This is a stand-alone attribute which indicates the element is initially non-functional.

Values: NA (HTML); disabled (XHTML)

Href

[2|3|3.2|4] [X1|X1.1] [IE1|M1|N1|O2.1]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This attribute indicates the URL to be loaded when the hyperlinked object is activated. Either this attribute or the NAME attribute MUST be present in the A tag.

Values: CDATA. [Either an absolute or relative URL. All URLs should be URL encoded where required.]

Hreflang

[2|3|3.2|4] [X1|X1.1] [IE|M|N6.1|O]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This attribute specifies the base language of the resource indicated in the HREF attribute.

Values: Any RFC 1766 value. [Must begin with a letter ([A-Za-z]), followed by any number of characters in [A-Za-z0-9-_:.]

Methods

[2|3|3.2|4] [X1|X1.1] [IE4|M|N|O]

Standards Details: NA

Required? No

Description:
This attribute should specify methods to be used in accessing the destination, as a whitespace-separated list of names. For similar reasons as for the TITLE attribute, it may be useful to include the information in advance in the link. For example, the browser may choose a different rendering display (possibly a special icon) for a destination that is searchable. None of the popular browsers ever implemented this attribute and it has since disappeared from the HTML 3.2 recommendation.

Values: The set of applicable names is a function of the protocol scheme of the URL in the HREF attribute.

Name

[2|3|3.2|4] [X1|X1.1] [IE1|M1|N1|O2.1]

Standards Details: In all HTML 4.x/XHTML 1.0 DTDs. Dropped in XHTML 1.1 in favor of ID attribute.

Required? No

Description:
This attribute assigns a symbolic name to the enclosed object (text, image, etc.) in order to use it as a destination in a hyperlink or other URL call. Either this attribute or the HREF attribute MUST be present in the A element. (Note: HTML 4 states that if ID and NAME are both used in a given A element, they should have the exact same value since they share the same domain value space.)

Values: CDATA

Rel

[2|3|3.2|4] [X1|X1.1] [IE3|M|N6.1|O6]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
The REL attribute is meant to give the relationship(s) described by the hyperlink.

Values: CDATA. [A whitespace separated list of relationship names.]

Rev

[2|3|3.2|4] [X1|X1.1] [IE|M3|N6.1|O]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
The REV attribute is meant to be the same as the REL attribute, but the semantics of the relationship are in the reverse direction. A link from A to B with REL="X" expresses the same relationship as a link from B to A with REV="X". An anchor may have both REL and REV attributes.

Values: CDATA. [A whitespace separated list of relationship names.]

SDAPref

[2|3|3.2|4] [X1|X1.1] [IE|M|N|O]

Standards Details: NA

Required? No

Description:
This is an SGML Document Access (SDA) attribute. SDA attributes are designed to transform HTML (and other SGML-based documents) to the ICADD DTD - which is used in creating accessible documents for users with visual disabilities (rendering in Braille, large print, speech synthesis, etc.) The attribute value specifies content to be added BEFORE the original element content (in this case the string "<Anchor: #AttList >") when the SDA document is rendered (SDA also allows attributes and values from the original element to be used in the new SDA element where necessary.) #Attlist lists out all of the attribute="value" pairs from the original code.

Value: "<Anchor: #AttList >"

Shape

[2|3|3.2|4] [X1|X1.1] [IE|M|N6|O7]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
The SHAPE attribute defines the type of region to be defined for mapping in the current AREA tag. The value specified here decides the number of coordinates to list in the COORDS attribute. If the SHAPE attribute is absent the shape is assumed to be of type RECT

Suppress

[2|3|3.2|4] [X1|X1.1] [IE|M|N4-4.x|O]

Standards Details: NA

Required? No

Description:
This attribute specifies that the dotted focus rectangle for this element should be suppressed when the hyperlink has keyboard focus.

Values: FALSE [DEFAULT] | TRUE

Tabindex

[2|3|3.2|4] [X1|X1.1] [IE4B1|M|N6|O7]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
"Tabbing" is a method of giving access/focus to an active HTML element using a standard keyboard sequence. All the active elements in a document can be cycled through using this sequence (ex: Windows TAB key.) The order of the active elements in this cycle is usually the order they occur in the document, but the TABINDEX attribute allows a different order to be established. The use of this attribute should create the following tabbing order cycle if the browser supports the attribute:

Active elements using the TABINDEX attribute with positive integers are navigated first. Low values are navigated first.
Active elements not specifying any TABINDEX attribute

Those elements carrying a DISABLED attribute or using negative TABINDEX values do not participate in the tabbing cycle.

Values: Positive or negative integers.

Target

[2|3|3.2|4] [X1|X1.1] [IE3A1|M|N2|O2.1]

Standards Details: Transitional/Frameset HTML 4.x/XHTML 1.0 DTDs only. Dropped in XHTML 1.1.

Required? No

Description:
This attribute specifies the named frame for the HREF hyperlink to jump to when activated.

Values: CDATA. [The TARGET reserved names apply.]

Title

[2|3|3.2|4] [X1|X1.1] [IE4B1|M|N6B2|O3]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This attribute suggests a title (advisory only) for the destination resource. The TITLE attribute may be used for display prior to accessing the destination resource (such as in a margin note or in a pop-up box while the mouse is over the hyperlink), or for resources that do not include titles (like graphics, plain text documents or Gopher menus.)

Values: CDATA

Type

[2|3|3.2|4] [X1|X1.1] [IE|M|N6.1|O]

Standards Details: In all HTML 4.x/XHTML DTDs

Required? No

Description:
This attribute specifies the MIME type of the resource indicated in the HREF attribute.

Values: CDATA. [Alphanumeric MIME type]

URN

[2|3|3.2|4] [X1|X1.1] [IE4|M|N|O]

Standards Details: NA

Required? No

Description:
This attribute was originally meant to specify a more persistent identifier for the NAME value of the hyperlink, but none of the popular browsers ever implemented this attribute. It has since disappeared from the HTML 3.2 recommendation.

Values: NA

Example
Hyperlink to a document:: <a href="http://www.foo.com/index.html" target="frame1">
Link text that leads to index.html at www.foo.com
</a>
Hyperlink to a Bookmark in the current document:: <a href="#Bookmark1" target="frame1">
Link text that leads to Bookmark1 in the current document
</a>
Hyperlink to a Bookmark in an external document:: <a href="http://www.foo.com/index.html#Bookmark1" target="frame1">
Link text that leads to Bookmark1 in index.html at www.foo.com
</a>
Image map/Shaped hyperlink list in an OBJECT element:: <object type="image/gif" data="http://www.foo.com/bigimage.gif" height="50" width="100">
Menu: 
<a href="http://www.foo.com/link1.html" shape="RECT" coords="0, 0, 50, 50">Link text 1</a> 
<a href="http://www.foo.com/link2.html" shape="RECT" coords="50, 0, 100, 50">Link text 2</a> 
</object>

Parent Model: %In-line Parent% | %Block Parent%
Exceptions: <a>
Content Model: %In-line Content%
Exceptions: <a>

Tips & Tricks

Remember when creating an ISMap that the IMG element must have the ISMAP attribute and be inside a hyperlink to the external map file.
Although these pages lists A HREF and A NAME separately in order to emphasize the distinction in functionality between these two aspects of the A element, the HREF and NAME attributes can co-exist in the same tag to serve as both a jump point and a destination for a jump point.
If you are using frames, be sure all hyperlinks in your sub-documents have targets which indicate the desired destination frames.
A commonly agreed-upon style issue is to make sure your hyperlink text is descriptive. It is considered good practice to integrate hyperlinks as seamlessly as possible into runs of text instead of using something like the very obvious qualifier: "Click Here"
The TITLE attribute is listed on this page both under the "Common Attributes" and "Specific Attributes" categories - I generally consider TITLE to be a "Common Attribute", but in the special case of the A and LINK elements, this attribute was included in the HTML standards at least as far back as HTML 2.0 - long before these attributes were specified for any other element.
DTD Note: A reader pointed out to me that it is also legal to use an A element without a NAME or HREF attribute (eg: <a TITLE="hello">content</a>) but I don't have any idea why an author might wish to do this.
NOTE: An additional method of invoking JavaScript exists using the A HREF element combined with Script code in place of the destination URL. The script code (either inline or externally referenced) is executed when the user clicks on the hyperlink.

Syntax: [script-engine]:[script-code]
Where [script-engine] is the name of the scripting language used, and [script-code] is either in-line script code or script code referenced elsewhere in the document.
Example: (displays an alert message box that contains the text 'hi there')
<a HREF="JavaScript:alert('hi there')">Click me to see a message.</a>
"How do you override the underlining of hyperlinks?" - Here is a document that addresses this common question.
URL Encoding:
URLs only allow a subset of allowable ISO-8859-1 (ISO-Latin) characters to be used. Any other characters must be encoded using a special escape syntax that uses combinations of the allowable subset. A separate page in the Topics section covers URL encoding in much greater detail, and even provides a little utility to automatically create URL encodings of characters.
Trivia?: One reader asked me what other hyperlink prefixes existed besides "mailto:" and "javascript:" - The following is not a definitive answer, but I did find one list of prefixes allowed in Netscape 4.x/6.x by browsing the Mozilla source code: "about:", "javascript:", "livescript:", "mailbox:", "mailto:", "mocha:", "news:", "pop3:", "snews:", "telnet:", "view-source:" and "wysiwyg:". It looks like IE supports "telnet:" and "view-source:" as well, but I don't know what ELSE it supports, or whether this information is or even "should be" useful to anyone. 8-}
Further on the previous point: One reader sent in a W3.org link on URI addressing schemes that attempts to be a definitive list (whether some of them work in any of the major browsers or not is left as an exercise for the reader to verify ;-})
More about shaped hyperlinks: If you're like me, shaped hyperlinks (those extra SHAPE and COORDS attributes) didn't make a lot of sense - the HTML spec doesn't go out of its way to explain why an author might choose to use these attributes.

At first blush, one might think that a shaped hyperlink could be used to define a single clickable sub-area within a hyperlinked object (such as an image;) You could perhaps also use A elements inside a MAP element instead of using AREA elements. A third scenario is using shaped hyperlinks within an OBJECT element to define a clickable map; it is this last which provides the interesting use-case in supporting browsers. This case acts like a MAP/USEMAP scenario for an image, and the regular hyperlinks themselves are not displayed (because they are nested in the OBJECT element.) In this case though, the shape map is for an OBJECT region and it degrades better to non-supporting browsers better than USEMAP-imagemaps can. For browsers that can not support rendering the OBJECT as specified, you are left with a simple and very usable list of hyperlinks. See the example above.

Browser Peculiarities

[Test] When jumping to a bookmark/fragment URL in the last viewable screen/page of a page that is longer than one screen, Internet Explorer versions up to and including 3.0 scroll such that the bookmark is at the top of the page, leaving blank space at the end of the document. This displays the document in a position that is not possible to achieve using scrollbar controls. Internet Explorer 4.0 and all Netscape versions display the document as low as it can normally be scrolled and no more.
[Test] Netscape 4.x has a bug: A location in a document can be defined using the ID attribute as well as the A NAME element. In Netscape 4.x this can be accessed using hyperlinks from external documents, but if the hyperlink is within the same document, the link does nothing.
Internet Explorer 4+ and Netscape 6+ implements TITLE as a hovering tooltip while Opera 3.x+ implements it as both a tooltip and a caption in the browser toolbar area.
[Test] IE4+ uses the TITLE attribute as the Favorites label for a URL when placed via the right-mouseclick context menu.
[Test] A brief history of FONT COLOR and A HREF interaction behavior:

Netscape 2,3:
Coloring Hyperlinks only works if the FONT COLOR is applied INSIDE the hyperlink, and ONLY if both are INSIDE a table cell.
Internet Explorer 1, 2, 3, Netscape 4.0 Beta 1-3, Opera:
Coloring hyperlinks does not work at all.
Internet Explorer 4.0, Netscape 4.0 Beta 4+:
Coloring hyperlinks works anywhere (not just inside tables) if the FONT COLOR is applied INSIDE the hyperlink.
[Test] Netscape 4.x can not correctly hyperlink to a bookmark (A NAME) that is nested inside a LAYER element from another document. It succeeds in jumping to the document, and it does attempt to jump within the document, but I didn't see a particular pattern to where it was jumping to...but it isn't the correct location. Hyperlinking to a bookmark nested in a LAYER from within the same document appears to work correctly.
I list the METHODS, REL, REV and URN attributes as being supported in IE based only upon Microsoft's documentation. While this data might be reachable via the DOM, these attributes certainly do not have any default presentational results.
The HREFLANG/REL/REV/TYPE attributes are exposed in Netscape 6.1+ by invoking a context menu on the hyperlink (PC: right clicking) and choosing "properties."

Hyperlink[A Href]

Hyperlink
[A Href]