Hyperlink
Encyclopedia
In computing
, a hyperlink (or link) is a reference
to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext
is text with hyperlinks. A software system for viewing and creating hypertext is a hypertext system, and to create a hyperlink is to hyperlink (or simply to link). A user following hyperlinks is said to navigate or browse the hypertext.
A hyperlink has an anchor, which is the location within a document from which the hyperlink can be followed; the document containing a hyperlink is known as its source document. to webpages. For example, in an online reference work such as Wikipedia
, many words and terms in the text are hyperlinked to definitions of those terms. Hyperlinks are often used to implement reference mechanisms, such as tables of contents, footnotes, bibliographies, indexes, letters and glossaries.
In some hypertext, hyperlinks can be bidirectional: they can be followed in two directions, so both ends act as anchors and as targets. More complex arrangements exist, such as many-to-many links.
The effect of following a hyperlink may vary with the hypertext system and may sometimes depend on the link itself; for instance, on the World Wide Web, most hyperlinks cause the target document to replace the document being displayed, but some are marked to cause the target document to open in a new window. Another possibility is transclusion
, for which the link target is a document fragment that replaces the link anchor within the source document. Not only persons browsing the document follow hyperlinks; they may also be followed automatically by programs. A program that traverses the hypertext, following each
hyperlink and gathering all the retrieved documents is known as a Web spider or crawling
.
displays remote content without the need for embedding the content. The remote content may be accessed with or without the user selecting the link. For example, the image above is a document that can be viewed separately, but it is included into this page with an inline link.
An inline link may display a modified version of the content; for instance, instead of an image, a thumbnail
, low resolution
preview
, cropped
section, or magnified
section may be shown. The full content will then usually be available on demand, as is the case with print publishing
software – e.g. with an external link. This allows for smaller file sizes and quicker response to changes when the full linked content is not needed, as is the case when rearranging a page layout
.
in HTML), a designated, often irregular part of an image. One way to define it is by a list of coordinates that indicate its boundaries. For example, a political map of Africa may have each country hyperlinked to further information about that country. A separate invisible hot area interface allows for swapping skins
or labels within the linked hot areas without repetitive embedding of links in the various skin elements.
saw the possibility of using hyperlinks to link any information to any other information over the Internet
. Hyperlinks were therefore integral to the creation of the World Wide Web
. Web pages are written in the hypertext mark-up language HTML
.
Links are specified in HTML using the <a> (anchor) elements.
To see the HTML used to create a page, most browsers offer a "view page source" option. Included in the HTML code will be an expression in the form symbol "" marking the start of an anchor, followed by the highlighted text and the "" symbol, which indicates the end of the source anchor. The element can also be used to indicate the target of a link.
Webgraph
is a graph
, formed from web page
s as vertices and hyperlinks, as directed edges.
describes hyperlinks that offer a far greater degree of functionality than those offered in HTML. These extended links can be multidirectional, linking from, within, and between XML documents. It also describes simple links, which are unidirectional and therefore offer no more functionality than hyperlinks in HTML.
s, PDF documents
, help systems such as Windows Help, word processing
documents, spreadsheets, Apple
's HyperCard
and many other places.
networks, including those which utilize the OpenSimulator
and Open Cobalt
platforms.
s may use HML-type hyperlinks, lightweight markup language
s of wikis (wiki markup) provide simplified syntax, called wikilinks for linking pages within wiki environments.
The syntax and appearance of wikilinks may vary. Ward Cunningham
's original wiki software
, the WikiWikiWeb
, used CamelCase
for this purpose. CamelCase was also used in the early version of Wikipedia
and is still used in some wikis, such as JSPWiki
, TiddlyWiki
, Trac
and PMWiki
. A common markup is using double square brackets around the term to be wikilinked, for example, the following input:wiki software
— will be converted by wiki software to look like this: wiki software
.
Hyperlinks used in wikis are commonly classified as follows:
If an internal wikilink leads to a page that does not exist, it usually has a distinct visual appearance. For example, in Wikipedia they are commonly displayed in red color, like this, and therefore they are called red links in Wikipedia. Another way is to display a highlighted clickable question mark by the wikilinked term, like this?.
The most common destination anchor is a URL
used in the World Wide Web
. This can refer to a document, e.g. a webpage, or other resource, or to a position in a webpage. The latter is achieved by means of an HTML element
with a "name" or "id" attribute at that position of the HTML document. The URL of the position is the URL of the webpage with a fragment identifier
— "#attribute name" — appended.
When linking to PDF documents from an HTML page the "attribute name" can be replaced with syntax that references a page number or another element of the PDF, for example, page=[pageNo] – "#page=386".
usually displays a hyperlink in some distinguishing way, e.g. in a different color
, font
or style
. The behavior and style of links can be specified using the Cascading Style Sheets
(CSS) language. In a graphical user interface, the appearance of a mouse cursor
may change into a hand
motif to indicate a link. In most graphical web browsers, links are displayed in underlined blue text when not cached, but underlined purple text when cached. When the user
activates the link (e.g. by clicking on it with the mouse) the browser will display the target of the link. If the target is not an HTML file, depending on the file type and on the browser and its plugins, another program may be activated to open the file. The HTML code contains some or all of the five main characteristics of a link: *link destination ("href" pointing to a URL) *link label
*link title *link target *link class or link id It uses the HTML element "a" with the attribute "href" (HREF is an abbreviation for "Hypertext REFerence") and optionally also the attributes "title", "target", and "class
" or "id": :<a href="URL" title="link title" target="link target" class="link class">link label</a> Example: To embed a link into a Page, blogpost, or comment, it may take this form: :
s: Example This contributes to a clean, easy to read text or document. When the cursor hovers over a link, depending on the browser and/or graphical user interface, some informative text about the link can be shown, popping up, not in a regular window
, but in a special hover
box, which disappears when the cursor is moved away (sometimes it disappears anyway after a few seconds, and reappears when the cursor is moved away and back). Mozilla Firefox
, IE
, Opera
, and many other web browsers all show the URL. In addition, the URL is commonly shown in the status bar
. Normally, a link will open in the current frame
or window, but sites that use frames and multiple windows for navigation can add a special "target" attribute to specify where the link will be loaded. If no window exists with that name, a new window will be created with the ID, which can be used to refer to the window later in the browsing session. Some developers may choose to capitalize links, to reflect server side interaction such as forms, or abbreviations. Capitalizing is OKAY. Creation of new windows is probably the most common use of the "target" attribute. In order to prevent accidental reuse of a window, the special window names "_blank" and "_new" are usually available, and will always cause a new window to be created. It is especially common to see this type of link when one large website links to an external page. The intention in that case is to ensure that the person browsing is aware that there is no endorsement of the site being linked to by the site that was linked from. However, the attribute is sometimes overused and can sometimes cause many windows to be created even while browsing a single site. Another special page name is "_top", which causes any frames in the current window to be cleared away so that browsing can continue in the full window.
at the start of Project Xanadu
. Nelson had been inspired by "As We May Think
", a popular essay by Vannevar Bush
. In the essay, Bush described a microfilm-based machine (the Memex
) in which one could link any two pages of information into a "trail" of related information, and then scroll back and forth among pages in a trail as if they were on a single microfilm reel.
In a series of books and articles published from 1964 through 1980, Nelson transposed Bush's concept of automated cross-referencing into the computer context, made it applicable to specific text strings rather than whole pages, generalized it from a local desk-sized machine to a theoretical worldwide computer network, and advocated the creation of such a network. Meanwhile, working independently, a team led by Douglas Engelbart
(with Jeff Rulifson
as chief programmer
) was the first to implement the hyperlink concept for scrolling within a single document (1966), and soon after for connecting between paragraphs within separate documents (1968), with NLS
.
A database program HyperCard
was released in 1987 for the Apple Macintosh that allowed hyperlinking between various types of pages within a document.
, some websites object to being linked to from other websites; some have claimed that linking to them is not allowed without permission.
Contentious in particular are deep links
, which do not point to a site's home page or other entry point designated by the site owner, but to content elsewhere, allowing the user to bypass the site's own designated flow, and inline links, which incorporate the content in question into the pages of the linking site, making it seem part of the linking site's own content unless an explicit attribution is added.
In certain jurisdictions it is or has been held that hyperlinks are not merely reference
s or citations, but are devices for copying web pages. In the Netherlands, Karin Spaink
was initially convicted in this way of copyright infringement by linking, although this ruling was overturned in 2003. The courts that advocate this view see the mere publication
of a hyperlink that connects to illegal material to be an illegal act in itself, regardless of whether referencing illegal material is illegal. In 2004, Josephine Ho
was acquitted of
'hyperlinks that corrupt traditional values' in Taiwan
.
In 2000 British Telecom sued Prodigy
, claiming that Prodigy infringed its patent on web hyperlinks. After litigation, a court
found for Prodigy, ruling that British Telecom's patent did not cover web hyperlinks.
In United States
jurisprudence
, there is a distinction between the mere act of linking to someone else's website, and linking to content that is illegal or infringing
. Several courts have found that merely linking to someone else's website is not copyright or trademark infringement, regardless of how much someone else might object. Linking to illegal or infringing content can be sufficiently problematic to give rise to legal liability. For a summary of the current status of US copyright law as to hyperlinking, see this discussion.
Computing
Computing is usually defined as the activity of using and improving computer hardware and software. It is the computer-specific part of information technology...
, a hyperlink (or link) is a reference
Reference (computer science)
In computer science, a reference is a value that enables a program to indirectly access a particular data item, such as a variable or a record, in the computer's memory or in some other storage device. The reference is said to refer to the data item, and accessing those data is called...
to data that the reader can directly follow, or that is followed automatically. A hyperlink points to a whole document or to a specific element within a document. Hypertext
Hypertext
Hypertext is text displayed on a computer or other electronic device with references to other text that the reader can immediately access, usually by a mouse click or keypress sequence. Apart from running text, hypertext may contain tables, images and other presentational devices. Hypertext is the...
is text with hyperlinks. A software system for viewing and creating hypertext is a hypertext system, and to create a hyperlink is to hyperlink (or simply to link). A user following hyperlinks is said to navigate or browse the hypertext.
A hyperlink has an anchor, which is the location within a document from which the hyperlink can be followed; the document containing a hyperlink is known as its source document. to webpages. For example, in an online reference work such as Wikipedia
Wikipedia
Wikipedia is a free, web-based, collaborative, multilingual encyclopedia project supported by the non-profit Wikimedia Foundation. Its 20 million articles have been written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site,...
, many words and terms in the text are hyperlinked to definitions of those terms. Hyperlinks are often used to implement reference mechanisms, such as tables of contents, footnotes, bibliographies, indexes, letters and glossaries.
In some hypertext, hyperlinks can be bidirectional: they can be followed in two directions, so both ends act as anchors and as targets. More complex arrangements exist, such as many-to-many links.
The effect of following a hyperlink may vary with the hypertext system and may sometimes depend on the link itself; for instance, on the World Wide Web, most hyperlinks cause the target document to replace the document being displayed, but some are marked to cause the target document to open in a new window. Another possibility is transclusion
Transclusion
In computer science, transclusion is the inclusion of a document or part of a document into another document by reference.For example, an article about a country might include a chart or a paragraph describing that country's agricultural exports from a different article about agriculture...
, for which the link target is a document fragment that replaces the link anchor within the source document. Not only persons browsing the document follow hyperlinks; they may also be followed automatically by programs. A program that traverses the hypertext, following each
hyperlink and gathering all the retrieved documents is known as a Web spider or crawling
Web crawler
A Web crawler is a computer program that browses the World Wide Web in a methodical, automated manner or in an orderly fashion. Other terms for Web crawlers are ants, automatic indexers, bots, Web spiders, Web robots, or—especially in the FOAF community—Web scutters.This process is called Web...
.
Inline link
An inline linkInline linking
Inline linking is the use of a linked object, often an image, from one site by a web page belonging to a second site...
displays remote content without the need for embedding the content. The remote content may be accessed with or without the user selecting the link. For example, the image above is a document that can be viewed separately, but it is included into this page with an inline link.
An inline link may display a modified version of the content; for instance, instead of an image, a thumbnail
Thumbnail
Thumbnails are reduced-size versions of pictures, used to help in recognizing and organizing them, serving the same role for images as a normal text index does for words...
, low resolution
Image resolution
Image resolution is an umbrella term that describes the detail an image holds. The term applies to raster digital images, film images, and other types of images. Higher resolution means more image detail....
preview
Preview (computing)
Preview is a computing function to display a document, page, or film before it is produced in its final form. In the case of printed material this is known as "print preview".- Contents Preview :...
, cropped
Cropping (image)
Cropping refers to the removal of the outer parts of an image to improve framing, accentuate subject matter or change aspect ratio. Depending on the application, this may be performed on a physical photograph, artwork or film footage, or achieved digitally using image editing software...
section, or magnified
Magnification
Magnification is the process of enlarging something only in appearance, not in physical size. This enlargement is quantified by a calculated number also called "magnification"...
section may be shown. The full content will then usually be available on demand, as is the case with print publishing
Desktop publishing
Desktop publishing is the creation of documents using page layout software on a personal computer.The term has been used for publishing at all levels, from small-circulation documents such as local newsletters to books, magazines and newspapers...
software – e.g. with an external link. This allows for smaller file sizes and quicker response to changes when the full linked content is not needed, as is the case when rearranging a page layout
Page layout
Page layout is the part of graphic design that deals in the arrangement and style treatment of elements on a page.- History and development :...
.
Anchor
An anchor hyperlink is a link bound to a portion of a document—generally text, though not necessarily. For instance, it may also be a hot area in an image (image mapImage map
In HTML and XHTML , an image map is a list of coordinates relating to a specific image, created in order to hyperlink areas of the image to various destinations . For example, a map of the world may have each country hyperlinked to further information about that country...
in HTML), a designated, often irregular part of an image. One way to define it is by a list of coordinates that indicate its boundaries. For example, a political map of Africa may have each country hyperlinked to further information about that country. A separate invisible hot area interface allows for swapping skins
Skin (computing)
In computing, a skin is a custom graphical appearance achieved by the use of a graphical user interface that can be applied to specific software and websites to suit the purpose, topic, or tastes of different users....
or labels within the linked hot areas without repetitive embedding of links in the various skin elements.
Hyperlinks in HTML
Tim Berners-LeeTim Berners-Lee
Sir Timothy John "Tim" Berners-Lee, , also known as "TimBL", is a British computer scientist, MIT professor and the inventor of the World Wide Web...
saw the possibility of using hyperlinks to link any information to any other information over the Internet
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
. Hyperlinks were therefore integral to the creation of the World Wide Web
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
. Web pages are written in the hypertext mark-up language HTML
HTML
HyperText Markup Language is the predominant markup language for web pages. HTML elements are the basic building-blocks of webpages....
.
Links are specified in HTML using the <a> (anchor) elements.
To see the HTML used to create a page, most browsers offer a "view page source" option. Included in the HTML code will be an expression in the form symbol "
Webgraph
Webgraph
The webgraph describes the directed links between pages of the World Wide Web. A graph, in general, consists of several vertices, some pairs connected by edges. In a directed graph, edges are directed lines or arcs...
is a graph
Graph (mathematics)
In mathematics, a graph is an abstract representation of a set of objects where some pairs of the objects are connected by links. The interconnected objects are represented by mathematical abstractions called vertices, and the links that connect some pairs of vertices are called edges...
, formed from web page
Web page
A web page or webpage is a document or information resource that is suitable for the World Wide Web and can be accessed through a web browser and displayed on a monitor or mobile device. This information is usually in HTML or XHTML format, and may provide navigation to other web pages via hypertext...
s as vertices and hyperlinks, as directed edges.
XLink: hyperlinks in XML
The W3C Recommendation called XLinkXLink
XML Linking Language, or XLink, is an XML markup language and W3C specification that provides methods for creating internal and external links within XML documents, and associating metadata with those links.-The XLink specification:...
describes hyperlinks that offer a far greater degree of functionality than those offered in HTML. These extended links can be multidirectional, linking from, within, and between XML documents. It also describes simple links, which are unidirectional and therefore offer no more functionality than hyperlinks in HTML.
Hyperlinks in other document technologies
Hyperlinks are used in the Gopher protocol, text editorText editor
A text editor is a type of program used for editing plain text files.Text editors are often provided with operating systems or software development packages, and can be used to change configuration files and programming language source code....
s, PDF documents
Portable Document Format
Portable Document Format is an open standard for document exchange. This file format, created by Adobe Systems in 1993, is used for representing documents in a manner independent of application software, hardware, and operating systems....
, help systems such as Windows Help, word processing
Word processing
Word processing is the creation of documents using a word processor. It can also refer to advanced shorthand techniques, sometimes used in specialized contexts with a specially modified typewriter.-External links:...
documents, spreadsheets, Apple
Apple Computer
Apple Inc. is an American multinational corporation that designs and markets consumer electronics, computer software, and personal computers. The company's best-known hardware products include the Macintosh line of computers, the iPod, the iPhone and the iPad...
's HyperCard
HyperCard
HyperCard is an application program created by Bill Atkinson for Apple Computer, Inc. that was among the first successful hypermedia systems before the World Wide Web. It combines database capabilities with a graphical, flexible, user-modifiable interface. HyperCard also features HyperTalk, written...
and many other places.
Hyperlinks in virtual worlds
Hyperlinks are being implemented in various 3D virtual worldVirtual world
A virtual world is an online community that takes the form of a computer-based simulated environment through which users can interact with one another and use and create objects. The term has become largely synonymous with interactive 3D virtual environments, where the users take the form of...
networks, including those which utilize the OpenSimulator
OpenSimulator
OpenSimulator is an open-source server platform for hosting virtual worlds. It is compatible with the client for Second Life and can host alternative worlds with differing feature sets with multiple protocols.-Features:...
and Open Cobalt
Open Cobalt
Open Cobalt is a free and open source software platform for constructing, accessing, and sharing virtual world both on local area networks or across the Internet, without any requirement for centralized servers....
platforms.
Hyperlinks in wikis
While wikiWiki
A wiki is a website that allows the creation and editing of any number of interlinked web pages via a web browser using a simplified markup language or a WYSIWYG text editor. Wikis are typically powered by wiki software and are often used collaboratively by multiple users. Examples include...
s may use HML-type hyperlinks, lightweight markup language
Lightweight markup language
A lightweight markup language is a markup language with a simple syntax, designed to be easy for a human to enter with a simple text editor, and easy to read in its raw form....
s of wikis (wiki markup) provide simplified syntax, called wikilinks for linking pages within wiki environments.
The syntax and appearance of wikilinks may vary. Ward Cunningham
Ward Cunningham
Howard G. "Ward" Cunningham is an American computer programmer who developed the first wiki. A pioneer in both design patterns and Extreme Programming, he started programming the software WikiWikiWeb in 1994 and installed it on the website of his software consultancy, Cunningham & Cunningham , on...
's original wiki software
Wiki software
Wiki software is collaborative software that runs a wiki, i.e., a website that allows users to create and collaboratively edit web pages via a web browser. A wiki system is usually a web application that runs on one or more web servers...
, the WikiWikiWeb
WikiWikiWeb
WikiWikiWeb is a term that has been used to refer to four things: the first wiki, or user-editable website, launched on 25 March 1995 by Ward Cunningham as part of the Portland Pattern Repository ; the Perl-based application that was used to run it, also developed by Cunningham, which was the first...
, used CamelCase
CamelCase
CamelCase , also known as medial capitals, is the practice of writing compound words or phrases in which the elements are joined without spaces, with each element's initial letter capitalized within the compound and the first letter either upper or lower case—as in "LaBelle", "BackColor",...
for this purpose. CamelCase was also used in the early version of Wikipedia
Wikipedia
Wikipedia is a free, web-based, collaborative, multilingual encyclopedia project supported by the non-profit Wikimedia Foundation. Its 20 million articles have been written collaboratively by volunteers around the world. Almost all of its articles can be edited by anyone with access to the site,...
and is still used in some wikis, such as JSPWiki
JSPWiki
JSPWiki is wiki software built around the standard J2EE components of Java, servlets and JSP. It was written by Janne Jalkanen and released under the LGPL. It is currently undergoing incubation with Apache and its license has been changed to the Apache License. The Sun Java System Portal Server...
, TiddlyWiki
TiddlyWiki
TiddlyWiki is an open source single page application wiki. A single HTML file contains CSS, JavaScript, and the content. The content is divided into a series of sections, or Tiddlers. A user is encouraged to read a TiddlyWiki by following links rather than sequentially scrolling down the...
, Trac
Trac
Trac is an open source, web-based project management and bug-tracking tool. The program is inspired by CVSTrac, and was originally named svntrac due to its ability to interface with Subversion. It is developed and maintained by Edgewall Software....
and PMWiki
PmWiki
PmWiki is wiki software written by Patrick R. Michaud in the PHP programming language. It is free software, licensed under the terms of the GNU General Public License.-Design focus:...
. A common markup is using double square brackets around the term to be wikilinked, for example, the following input:
Wiki software
Wiki software is collaborative software that runs a wiki, i.e., a website that allows users to create and collaboratively edit web pages via a web browser. A wiki system is usually a web application that runs on one or more web servers...
Wiki software
Wiki software is collaborative software that runs a wiki, i.e., a website that allows users to create and collaboratively edit web pages via a web browser. A wiki system is usually a web application that runs on one or more web servers...
.
Hyperlinks used in wikis are commonly classified as follows:
- Internal wikilinks or intrawiki links lead to pages within the same wiki website.
- Interwiki links are simplified markup hyperlinks lead to pages of other wikis.
- External links lead to other webpages.
If an internal wikilink leads to a page that does not exist, it usually has a distinct visual appearance. For example, in Wikipedia they are commonly displayed in red color, like this, and therefore they are called red links in Wikipedia. Another way is to display a highlighted clickable question mark by the wikilinked term, like this?.
How hyperlinks work in HTML
A link from one domain to another is said to be outbound from its source anchor and inbound to its target.The most common destination anchor is a URL
Uniform Resource Locator
In computing, a uniform resource locator or universal resource locator is a specific character string that constitutes a reference to an Internet resource....
used in the World Wide Web
World Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
. This can refer to a document, e.g. a webpage, or other resource, or to a position in a webpage. The latter is achieved by means of an HTML element
HTML element
An HTML element is an individual component of an HTML document. HTML documents are composed of a tree of HTML elements and other nodes, such as text nodes. Each element can have attributes specified. Elements can also have content, including other elements and text. HTML elements represent...
with a "name" or "id" attribute at that position of the HTML document. The URL of the position is the URL of the webpage with a fragment identifier
Fragment identifier
In computer hypertext, a fragment identifier is a short string of characters that refers to a resource that is subordinate to another, primary resource...
— "#attribute name" — appended.
When linking to PDF documents from an HTML page the "attribute name" can be replaced with syntax that references a page number or another element of the PDF, for example, page=[pageNo] – "#page=386".
Link behavior in web browsers
A web browserWeb browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
usually displays a hyperlink in some distinguishing way, e.g. in a different color
Color
Color or colour is the visual perceptual property corresponding in humans to the categories called red, green, blue and others. Color derives from the spectrum of light interacting in the eye with the spectral sensitivities of the light receptors...
, font
Font
In typography, a font is traditionally defined as a quantity of sorts composing a complete character set of a single size and style of a particular typeface...
or style
Typeface
In typography, a typeface is the artistic representation or interpretation of characters; it is the way the type looks. Each type is designed and there are thousands of different typefaces in existence, with new ones being developed constantly....
. The behavior and style of links can be specified using the Cascading Style Sheets
Cascading Style Sheets
Cascading Style Sheets is a style sheet language used to describe the presentation semantics of a document written in a markup language...
(CSS) language. In a graphical user interface, the appearance of a mouse cursor
Cursor (computers)
In computing, a cursor is an indicator used to show the position on a computer monitor or other display device that will respond to input from a text input or pointing device. The flashing text cursor may be referred to as a caret in some cases...
may change into a hand
Hand
A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...
motif to indicate a link. In most graphical web browsers, links are displayed in underlined blue text when not cached, but underlined purple text when cached. When the user
User (computing)
A user is an agent, either a human agent or software agent, who uses a computer or network service. A user often has a user account and is identified by a username , screen name , nickname , or handle, which is derived from the identical Citizen's Band radio term.Users are...
activates the link (e.g. by clicking on it with the mouse) the browser will display the target of the link. If the target is not an HTML file, depending on the file type and on the browser and its plugins, another program may be activated to open the file. The HTML code contains some or all of the five main characteristics of a link: *link destination ("href" pointing to a URL) *link label
Anchor text
The anchor text, link label or link text is the visible, clickable text in a hyperlink. The words contained in the anchor text can determine the ranking that the page will receive by search engines. Since 1998, some web browsers have added the ability to show a tooltip for a hyperlink before it is...
*link title *link target *link class or link id It uses the HTML element "a" with the attribute "href" (HREF is an abbreviation for "Hypertext REFerence") and optionally also the attributes "title", "target", and "class
Cascading Style Sheets
Cascading Style Sheets is a style sheet language used to describe the presentation semantics of a document written in a markup language...
" or "id": :<a href="URL" title="link title" target="link target" class="link class">link label</a> Example: To embed a link into a Page, blogpost, or comment, it may take this form: :
Example Web browser
A web browser is a software application for retrieving, presenting, and traversing information resources on the World Wide Web. An information resource is identified by a Uniform Resource Identifier and may be a web page, image, video, or other piece of content...
s: Example This contributes to a clean, easy to read text or document. When the cursor hovers over a link, depending on the browser and/or graphical user interface, some informative text about the link can be shown, popping up, not in a regular window
Window
A window is a transparent or translucent opening in a wall or door that allows the passage of light and, if not closed or sealed, air and sound. Windows are usually glazed or covered in some other transparent or translucent material like float glass. Windows are held in place by frames, which...
, but in a special hover
Hover
Hover may refer to:*Hovering , the process by which an object is suspended by a physical force against gravity, in a stable position without solid physical contactIn transport* Hover , nearly stationary flight in a helicopter...
box, which disappears when the cursor is moved away (sometimes it disappears anyway after a few seconds, and reappears when the cursor is moved away and back). Mozilla Firefox
Mozilla Firefox
Mozilla Firefox is a free and open source web browser descended from the Mozilla Application Suite and managed by Mozilla Corporation. , Firefox is the second most widely used browser, with approximately 25% of worldwide usage share of web browsers...
, IE
Internet Explorer
Windows Internet Explorer is a series of graphical web browsers developed by Microsoft and included as part of the Microsoft Windows line of operating systems, starting in 1995. It was first released as part of the add-on package Plus! for Windows 95 that year...
, Opera
Opera (web browser)
Opera is a web browser and Internet suite developed by Opera Software with over 200 million users worldwide. The browser handles common Internet-related tasks such as displaying web sites, sending and receiving e-mail messages, managing contacts, chatting on IRC, downloading files via BitTorrent,...
, and many other web browsers all show the URL. In addition, the URL is commonly shown in the status bar
Status bar
A status bar, similar to a status line, is an information area typically found at the bottom of windows in a graphical user interface.A status bar is sometimes divided into sections, each of which shows different information. Its job is primarily to display information about the current state of...
. Normally, a link will open in the current frame
Framing (World Wide Web)
When using web browsers, the terms frames or frameset refer to the display of two or more web pages or media elements displayed side-by-side within the same browser window...
or window, but sites that use frames and multiple windows for navigation can add a special "target" attribute to specify where the link will be loaded. If no window exists with that name, a new window will be created with the ID, which can be used to refer to the window later in the browsing session. Some developers may choose to capitalize links, to reflect server side interaction such as forms, or abbreviations. Capitalizing is OKAY. Creation of new windows is probably the most common use of the "target" attribute. In order to prevent accidental reuse of a window, the special window names "_blank" and "_new" are usually available, and will always cause a new window to be created. It is especially common to see this type of link when one large website links to an external page. The intention in that case is to ensure that the person browsing is aware that there is no endorsement of the site being linked to by the site that was linked from. However, the attribute is sometimes overused and can sometimes cause many windows to be created even while browsing a single site. Another special page name is "_top", which causes any frames in the current window to be cleared away so that browsing can continue in the full window.
History of the hyperlink
The term "hyperlink" was coined in 1965 (or possibly 1964) by Ted NelsonTed Nelson
Theodor Holm Nelson is an American sociologist, philosopher, and pioneer of information technology. He coined the terms "hypertext" and "hypermedia" in 1963 and published it in 1965...
at the start of Project Xanadu
Project Xanadu
Project Xanadu was the first hypertext project, founded in 1960 by Ted Nelson. Administrators of Project Xanadu have declared it an improvement over the World Wide Web, with mission statement: "Today's popular software simulates paper...
. Nelson had been inspired by "As We May Think
As We May Think
As We May Think is an essay by Vannevar Bush, first published in The Atlantic Monthly in July 1945, and republished again as an abridged version in September 1945 — before and after the U.S. nuclear attacks on Japan...
", a popular essay by Vannevar Bush
Vannevar Bush
Vannevar Bush was an American engineer and science administrator known for his work on analog computing, his political role in the development of the atomic bomb as a primary organizer of the Manhattan Project, the founding of Raytheon, and the idea of the memex, an adjustable microfilm viewer...
. In the essay, Bush described a microfilm-based machine (the Memex
Memex
The memex is the name given by Vannevar Bush to the hypothetical proto-hypertext system he described in his 1945 The Atlantic Monthly article As We May Think...
) in which one could link any two pages of information into a "trail" of related information, and then scroll back and forth among pages in a trail as if they were on a single microfilm reel.
In a series of books and articles published from 1964 through 1980, Nelson transposed Bush's concept of automated cross-referencing into the computer context, made it applicable to specific text strings rather than whole pages, generalized it from a local desk-sized machine to a theoretical worldwide computer network, and advocated the creation of such a network. Meanwhile, working independently, a team led by Douglas Engelbart
Douglas Engelbart
Douglas Carl Engelbart is an American inventor, and an early computer and internet pioneer. He is best known for his work on the challenges of human-computer interaction, resulting in the invention of the computer mouse, and the development of hypertext, networked computers, and precursors to GUIs...
(with Jeff Rulifson
Jeff Rulifson
Johns Frederick Rulifson is an American computer scientist.-Biography:Johns Frederick Rulifson was born August 20, 1941 in Bellefontaine, Ohio. His father was Erwin Charles Rulifson and mother was Virginia Helen Johns...
as chief programmer
Programmer
A programmer, computer programmer or coder is someone who writes computer software. The term computer programmer can refer to a specialist in one area of computer programming or to a generalist who writes code for many kinds of software. One who practices or professes a formal approach to...
) was the first to implement the hyperlink concept for scrolling within a single document (1966), and soon after for connecting between paragraphs within separate documents (1968), with NLS
NLS (computer system)
NLS, or the "oN-Line System", was a revolutionary computer collaboration system designed by Douglas Engelbart and implemented by researchers at the Augmentation Research Center at the Stanford Research Institute during the 1960s...
.
A database program HyperCard
HyperCard
HyperCard is an application program created by Bill Atkinson for Apple Computer, Inc. that was among the first successful hypermedia systems before the World Wide Web. It combines database capabilities with a graphical, flexible, user-modifiable interface. HyperCard also features HyperTalk, written...
was released in 1987 for the Apple Macintosh that allowed hyperlinking between various types of pages within a document.
Legal issues
While hyperlinking among webpages is an intrinsic feature of the webWorld Wide Web
The World Wide Web is a system of interlinked hypertext documents accessed via the Internet...
, some websites object to being linked to from other websites; some have claimed that linking to them is not allowed without permission.
Contentious in particular are deep links
Deep linking
On the World Wide Web, deep linking is making a hyperlink that points to a specific page or image on a website, instead of that website's main or home page. Such links are called deep links.-Example:...
, which do not point to a site's home page or other entry point designated by the site owner, but to content elsewhere, allowing the user to bypass the site's own designated flow, and inline links, which incorporate the content in question into the pages of the linking site, making it seem part of the linking site's own content unless an explicit attribution is added.
In certain jurisdictions it is or has been held that hyperlinks are not merely reference
Reference
Reference is derived from Middle English referren, from Middle French rèférer, from Latin referre, "to carry back", formed from the prefix re- and ferre, "to bear"...
s or citations, but are devices for copying web pages. In the Netherlands, Karin Spaink
Karin Spaink
Karin Spaink is a journalist, writer and feminist.Spaink is a free speech advocate and social critic. Some of her battles include:* New-age writers who assert all diseases are only a psychological phenomenon;...
was initially convicted in this way of copyright infringement by linking, although this ruling was overturned in 2003. The courts that advocate this view see the mere publication
Publication
To publish is to make content available to the public. While specific use of the term may vary among countries, it is usually applied to text, images, or other audio-visual content on any medium, including paper or electronic publishing forms such as websites, e-books, Compact Discs and MP3s...
of a hyperlink that connects to illegal material to be an illegal act in itself, regardless of whether referencing illegal material is illegal. In 2004, Josephine Ho
Josephine Ho
Josephine Chuen-juei Ho is the chair of the English department ofNational Central University, Taiwan, and coordinator of its.She has withstood lawsuits directed at her outspokenness on gender and rights issues. She holds two doctorates from US universities. She has published many books.-External...
was acquitted of
'hyperlinks that corrupt traditional values' in Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
.
In 2000 British Telecom sued Prodigy
Prodigy (ISP)
Prodigy Communications Corporation was an online service that offered its subscribers access to a broad range of networked services, including news, weather, shopping, bulletin boards, games, polls, expert columns, banking, stocks, travel, and a variety of other features.Initially subscribers...
, claiming that Prodigy infringed its patent on web hyperlinks. After litigation, a court
Court
A court is a form of tribunal, often a governmental institution, with the authority to adjudicate legal disputes between parties and carry out the administration of justice in civil, criminal, and administrative matters in accordance with the rule of law...
found for Prodigy, ruling that British Telecom's patent did not cover web hyperlinks.
In United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
jurisprudence
Jurisprudence
Jurisprudence is the theory and philosophy of law. Scholars of jurisprudence, or legal theorists , hope to obtain a deeper understanding of the nature of law, of legal reasoning, legal systems and of legal institutions...
, there is a distinction between the mere act of linking to someone else's website, and linking to content that is illegal or infringing
Copyright infringement
Copyright infringement is the unauthorized or prohibited use of works under copyright, infringing the copyright holder's exclusive rights, such as the right to reproduce or perform the copyrighted work, or to make derivative works.- "Piracy" :...
. Several courts have found that merely linking to someone else's website is not copyright or trademark infringement, regardless of how much someone else might object. Linking to illegal or infringing content can be sufficiently problematic to give rise to legal liability. For a summary of the current status of US copyright law as to hyperlinking, see this discussion.
See also
- Dead link
- Internal linkInternal linkAn internal link is a hyperlink that is a reference or navigation element in a document to another section of the same document or to another document that may be on or part of the same website or domain of the internet....
- Methods of website linkingMethods of website linkingThis article pertains to methods of hyperlinking to/of different websites, often used in regard to search engine optimization . Many techniques and special terminology about linking are described below.-Reciprocal link:...
- Object hyperlinkingObject hyperlinkingObject hyperlinking is a neologism that usually refers to extending the Internet to objects and locations in the real world. The current Internet does not extend beyond the electronic world. Object hyperlinking aims to extend the Internet to the real world by attaching object tags with URLs as...
- PageRankPageRankPageRank is a link analysis algorithm, named after Larry Page and used by the Google Internet search engine, that assigns a numerical weighting to each element of a hyperlinked set of documents, such as the World Wide Web, with the purpose of "measuring" its relative importance within the set...
- Xenu's Link SleuthXenu's Link SleuthXenu, or Xenu's Link Sleuth, is a computer program that checks websites for broken hyperlinks. It is written by Tilman Hausherr and is proprietary software available at no charge. The program is named after Xenu, the Galactic Ruler from Scientology scripture.-Format:Link Sleuth runs on Microsoft...