Link

Link Support Key: [2\|3\|3.2\|4] [X1\|X1.1] [IE3B1\|M3\|N4B2\|O3.5]	What is it? Attributes Tag Example	Parent/Content Model Tips & Tricks Browser Peculiarities
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Quick Statistics
End Tag:		Omitted
Standards Details:		In all HTML 4.x/XHTML DTDs
XHTML Modules:		Link
CSS 'display' Type:		NA
CSS Mapping:		NA
Default Rendering:		NA
Official Docs:		HTML 4.x, XHTML 1.1

What is it?: The Link element is a special HEAD element utilizing many of the same attributes as the Hyperlink element [A]. It indicates a relationship between the current document and some other object. A document may have any number of LINK elements which can indicate authorship, related indices and glossaries, older or more recent versions, document hierarchy, associated resources such as style sheets, etc. Servers may also allow links to be added to a document by those who do not have the right to alter the body portion of a document. The popular browsers are just beginning to support this element, which has been in the HTML specifications for some time.

Some uses for LINK
Many of the following keywords are taken from the expired HTML 3.0 Draft. They describe a proposed standard set of relationships for use in documents. Details of browser support and examples are further down.
REL=Alternate StyleSheet: References an external Style Sheet [-->Index DOT Css] which can be used to control the way the current document is rendered, but will not be used by default if a "rel='stylesheet'" stylesheet is present and successfully loaded. Browsers may present an interface to enable switching between multiple stylesheets.
REL=Bookmark: These are used to provide direct links to key entry points into an extended document. The TITLE attribute may be used to label the bookmark. Several bookmarks may be defined in each document, and provide a means for orienting users in extended documents.
REL=Copyright: References a copyright statement for the current document.
REL=Fontdef: References a downloadable font definition file.
REL=Glossary: References a document providing a glossary of terms that pertain to the current document.
REL=Help: References a document offering help, e.g. describing the wider context and offering further links to relevant documents. This is aimed at reorienting users who have lost their way.
REL=Home: References a home page or the top of some hierarchy.
REL=Index: References a document providing an index for the current document.
REL=Next: References the next document to visit in a document structure or guided tour.
REL=Previous: References the previous document in a document structure or guided tour.
REL=Shortcut Icon: Associates an icon with the current page when favorite-d/bookmarked in your browser.
REL=StyleSheet: References an external Style Sheet [-->Index DOT Css] which is used to control the way the current document is rendered.
REL=ToC: References a document serving as a table of contents.
REL=Up: If the document is part of a hierarchy, this references the immediate parent of the current document.
Defining document specific toolbars
[IE|M3|N7|O7]: The LINK element can be used to define a toolbar of navigation buttons or an equivalent mechanism such as menu items. Many of the values for the REL attribute could be reserved for this purpose (such as Home, Next, Previous, etc.); Example:
<link title="Here is my home page" rel="HOME" href="myhome.htm" />
Link to an associated Style Sheet
[IE3B1|M|N4B2|O3.5]: The LINK element can be used with REL=StyleSheet to reference an external Style Sheet which is used to control the way the current document is rendered.; Example:
<link rel="STYLESHEET" href="http://www.company.com/mystyles.css" type="text/css" />
Link to an alternate Style Sheet
[IE|M|N6|O7]: The LINK element can be used with REL="Alternate StyleSheet" to reference additional Style Sheet resources to use for the current document. An alternate stylesheet may also be used if the REL="Stylesheet" stylesheet has trouble loading for some reason.; Example:
<link rel="ALTERNATE STYLESHEET" href="http://www.company.com/mystyles.css"
type="text/css" title="Alternate stylesheet1" />
Link to a Font Definition file
[IE|M|N4-4.x|O]: The LINK element can be used with REL=Fontdef to reference a downloadable font definition file.; Example:
<link rel="FONTDEF" src="http://www.example.com/fonts/downloadfont.pfr" />
Link to a Favorites icon
[IE4|M|N7|O7]: The LINK element can be used with REL="SHORTCUT ICON" to associate an icon image with the current page if it is bookmarked in a user's browser. More information on this process can be found here.; Example:
<link rel="SHORTCUT ICON" href="http://www.example.com/icons/mypageicon.ico" />

Common Attributes
%Core%: [2|3|3.2|4] [X1|X1.1] [IE4|M3|N6B1|O5]
%Accessibility%: [2|3|3.2|4] [X1|X1.1] [IE|M|N6|O7]
%Events%: [2|3|3.2|4] [X1|X1.1] [IE|M|N|O]
%Language%: [2|3|3.2|4] [X1|X1.1] [IE|M|N|O]
Specific Attributes
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.]
Disabled
[2|3|3.2|4] [X1|X1.1] [IE4|M|N|O]: Standards Details: NA; Required? No; Description:
This is a stand-alone attribute which indicates the linked dependency is initially non-functional.; Values: NA
Href
[2|3|3.2|4] [X1|X1.1] [IE3B1|M3|N4B2|O3.5]: Standards Details: In all HTML 4.x/XHTML DTDs; Required? No; Description:; This attribute indicates the URL of a document linked to the current document through relationships established by the other attributes of this element.; 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|N|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: CDATA. [RFC 1766 values.]
Language
[2|3|3.2|4] [X1|X1.1] [IE|M|N4-4.x|O]: Standards Details: NA; Required? No; Description:
This attribute indicates the scripting language the linked element is written in.; Values: Alphanumeric string representing a scripting language.
Media
[2|3|3.2|4] [X1|X1.1] [IE4|M|N4|O3.5]: Standards Details: In all HTML 4.x/XHTML DTDs; Required? No; Description:
This attribute is a keyword representing the intended rendering destination for the style sheet definitions. Multiple destinations are given delimited by commas.; Values:
CDATA. [Single or comma separated list of media keywords:
screen [DEFAULT] - style information should be used for rendering to computer screens.
print - style information should be used for rendering to page-centric devices, ie: printed paper or print preview screen modes.
projection - style information should be used for rendering to transparent projected media devices.
braille - style information should be used for rendering to braille devices.
speech - style information should be used for rendering to speech synthesizers.
all - style information should be used for rendering to all devices.]
Methods
[2|3|3.2|4] [X1|X1.1] [IE|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] [IE4|M|N|O]: Standards Details: NA; Required? No; Description:
This attribute specifies the name of the link so that scripting languages may access it.; Values: An alphanumeric string. Must begin with an alphabetic character.
Rel
[2|3|3.2|4] [X1|X1.1] [IE3B1|M3|N4B2|O3.5]: Standards Details: In all HTML 4.x/XHTML DTDs; Required? No; Description:; The REL attribute is meant to give the relationship(s) described between the current document and the document specified by the HREF attribute.; Values: CDATA. [A whitespace separated list of relationship names.]
Rev
[2|3|3.2|4] [X1|X1.1] [IE4|M3|N7|O]: Standards Details: In all HTML 4.x/XHTML DTDs; Required? No; Description:; The REV attribute is basically 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". A LINK tag 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 "Linked to : #AttVal (TITLE) (URN) (HREF)") 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.) "#AttVal (TITLE) (URN) (HREF)" references the values of the LINK TITLE, URN and HREF attributes, respectively, if present.; Value: "Linked to : #AttVal (TITLE) (URN) (HREF)"
Src
[2|3|3.2|4] [X1|X1.1] [IE|M|N4-4.x|O]: Standards Details: NA; Required? No; Description:
This attribute indicates the URL of a downloadable font definition file.; Values: Either an absolute or relative URL. All URLs should be URL encoded where required.
Target
[2|3|3.2|4] [X1|X1.1] [IE4|M|N7|O]: Standards Details: In Transitional and 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 browser to display the linked resource if activated by the system or user.; Values: CDATA. [The TARGET reserved names apply.]
Title
[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 attribute suggests a title (advisory only) for the destination resource. The TITLE attribute may be used for display prior to accessing the destination resource, 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] [IE3B1|M|N4B2|O]: Standards Details: In all HTML 4.x/XHTML DTDs; Required? No; Description:; This attribute represents the MIME type of the linked resource.; Values: CDATA. [(wrt style sheet usage) text/css, text/javascript]
URN
[2|3|3.2|4] [X1|X1.1] [IE|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 LINK, but none of the popular browsers ever implemented this attribute. It has since disappeared from the HTML 3.2 recommendation.; Values: NA

Example: <html>
<head>
     <title>Document Title</title>
     <link title="Here is my home page" rel="HOME" href="myhome.htm" />
     <link rel="STYLESHEET" href="http://www.company.com/mystyles.css" type="text/css" />
</head>
<body>
     Document content goes here.
</body>
</html>

Parent Model: <head>
Content Model: This element does not accept any content.

Tips & Tricks

The Mosaic implementation of the LINK element is not widely supported, even though many of the concepts for it have existed in HTML since version 2.0. Its use does not harm a document in any way, but it would be best not to rely on this as a sole navigation scheme until wider support exists.
Remember to use the TYPE attribute in relation to the use of the LINK element for Style Sheet purposes. With the advent of Netscape's Javascript Accessible Style Sheets, it never hurts to be explicit as to which style sheet language is being used.
The wide implementation of Style Sheets has begun with Internet Explorer 3.0 and has continued with its debut in Netscape version 4.0 and Opera 3.5. These browsers represent the vast majority of the total browser market, so use of CSS is not discouraged (it doesn't hurt that CSS is backward compatible with non-CSS browsers.)
The use of "Screen" as the default media in HTML 4.x is in direct conflict with the CSS standards. It should be "All."

Browser Peculiarities

Mosaic supports the LINK element in its 3.0 versions. All LINK REL navigation relationships will be rendered in a separate pane of the browser window.
IE 3.0 Beta 1 did not automatically register the MIME type for Style Sheets, so if you're using a linked style sheet, the server administrator on the user's site would have to register the "text/css" type on the server. This problem was fixed in later Internet Explorer versions.
Netscape 4.0 Beta 2 assumed a default MIME type for style sheets to be 'text/javascript' for Javascript accessible style sheets. This was fixed in beta 3 to the accepted 'text/css' default.
[Test] Internet Explorer 4.0 and 5.0 only support the 'screen', 'print' and 'all' MEDIA attribute values.
[Test] Netscape 4 supported only the 'screen' MEDIA attribute value. Netscape 6 appears to support the 'screen', 'print' and 'all' MEDIA attribute values.
[Test] Opera 3.5 only supports the 'screen', and 'all' MEDIA attribute values.
[Test] IE 3.0 only allowed for a single LINK or STYLE block. Only the last one specified in the document is used. IE 4.0 and above, Netscape and Opera merge/cascade multiple STYLE elements.
Although Internet Explorer 4.0 and above has access to the REV attribute through the DOM, it does not appear to do anything with this information.
[Test] Netscape 4.x ignores a LINKed stylesheet if the LINK element has an ID attribute.
Netscape's meager documentation on the SRC attribute says that the HREF attribute takes precedence if both attributes are present.
I am not sure if Netscape 6 supports dynamic fonts as it did in Netscape 4.x. If it does not, then the SRC attribute is definitely not supported in V6.0, since the other usage for SRC from 4.x (an alternate method of specifying an HREF) is not supported in 6.0.
Netscape's meager documentation on the Mozilla site also mentions two other attributes as valid: ARCHIVE and CODEBASE. I could not get either of these attributes to behave as expected though.
Netscape 6+ presents a list of alternate stylesheets in its user interface. The contents of the TITLE attribute are used for the display name of each stylesheet.
Netscape 6+ presents the list of LINK types via a context menu (PC: right click)...view page info...links tab. After Netscape 7, LINKs can be presented directly in the user interface via the "site navigation bar."