HTML and CSS Reference
In-Depth Information
for
Automatic Teller Machine
or
CSS
for
Cascading Style Sheets
, or from initials extracted from the
syllables of a long word, such as
DNA
for
deoxyribonucleic acid
(these are also called
initialisms
).
An
acronym
is a specific type of abbreviation, being a pronounceable word formed from the first letters of a
multiword phrase—
laser
from
light amplification by simulated emission of radiation
and
PIN
from
personal
identification number
—or the first portion of each word, as in
retcon
from
retroactive continuity
and
sysadmin
from
system administrator
.
Previous versions of HTML included an
acronym
element specifically for marking up acronyms as a
distinct type of abbreviation, but browser support for
acronym
is still inconsistent after all these years, and
web authors are often confused about when to use
abbr
or when to use
acronym
. HTML5 has eliminated
these problems by eliminating the
acronym
element altogether. Acronyms are abbreviations themselves,
so the more general
abbr
element covers acronyms as well.
Use the
abbr
element similarly to
dfn
to point out the defining instance of an abbreviation, the first time it's
introduced in a body of text. You can use the abbreviation in text thereafter without any special markup. Of
course, not every abbreviation needs to be called out: common ones such as
etc.
and
Inc.
probably don't
require explanation. Use your best judgment based on your understanding of the content and your
audience.
An
abbr
element can (and usually should) include the expanded form of the term in a
title
attribute. As
with the
dfn
element, if the abbreviation is explained in the regular text, expanding it in a
title
attribute
isn't necessary. However, if a
title
attribute is present, its value
must
be the expanded form of the
abbreviation and nothing else.
Listing 4-33 shows two ways to introduce an abbreviation in text.
Listing 4-33.
Abbreviations marked up with the
abbr
element
<blockquote>
<p>After the
<abbr title="Electro-Magnetic Pulse">EMP</abbr>
incapacitated
all my electronics, I feared I would be trapped on that rooftop without the
use of my anti-gravity belt. Luckily I still had my trusty Gravity-Assisted
Descent Grapple Extension Tool (
<abbr>GADGET</abbr>
) from Power Outfitters.
Its double-braided polyfiber construction is purely analog, and thus immune
to all electro-magnetic disturbances. I rappelled down with ease!</p>
</blockquote>
Some browsers (like Firefox for Mac, shown in Figure 4-20) display an
abbr
element with a dotted
underline if it carries a
title
attribute, and no decoration if the attribute is absent. Other browsers don't
apply any default styling to
abbr
elements at all. Most browsers
do
display the value of the
title
attribute
in a “tooltip” when the user's pointer lingers over the element, to reveal the extended form of an
abbreviation.