Up to this point, we've dealt with HTML and XHTML documents as
standalone entities, concentrating on the language elements you use
for structure and to format your work. The true power of these markup
languages, however, lies in their ability to join collections of
documents together into a full library of information and to link
your library of documents with other collections around the world.
Just as readers have considerable control over how the document looks
onscreen, with hyperlinks they also have control over the order of
presentation as they navigate through your information. It's
the "HT" in HTML and XHTML -- hypertext -- and
it's the twist that spins the Web.
6.1. Hypertext Basics
A fundamental
feature of hypertext is that you can hyperlink documents; you can
point to another place inside the current document, inside another
document in the local collection, or inside a document anywhere on
the Internet. The documents become an intricately woven web of
information. (Get the name analogy now?) The target document is
usually somehow related to and enriches the source; the linking
element in the source should convey that relationship to the reader.
Hyperlinks can be used for all kinds of effects. They can be used
inside tables of contents and lists of topics. With a click of the
mouse on their browser screen or a press of a key on their keyboard,
readers select and automatically jump to a topic of interest in the
same document or to another document located in an entirely different
collection somewhere around the world.
Hyperlinks also point readers to more information about a mentioned
topic. "For more information, see Kumquats on Parade,"
for example. Authors use hyperlinks to reduce repetitive information.
For instance, we recommend you sign your name to each of your
documents. Rather than include full contact information in each
document, a hyperlink connects your name to a single place that
contains your address, phone number, and so forth.
A hyperlink, or
anchor in standard
parlance, is marked by the <a> tag and comes
in two flavors. As we describe in detail later, one type of anchor
creates a hot spot in the document that, when activated and selected
(usually with a mouse) by the user, causes the browser to link. It
automatically loads and displays another portion of the same or
another document altogether, or triggers some Internet
service-related action, such as sending email or downloading a
special file. The other type of anchor creates a label, a place in a
document that can be referenced as a hyperlink.[36]
There also are some mouse-related events associated with hyperlinks, which, through JavaScript, let you incorporate some exciting effects.
