HTML and CSS Reference
In-Depth Information
unique, but multiple classes can be applied to a single element like tag-
ging in popular social network tools. Some examples are shown in the
following table.
Suggested meaning
A paragraph
<p id="author">
A paragraph that represents a particular author
<p class="bio">
A paragraph that represents a biography
<p class="author bio">
A paragraph that represents an author biography
No definitive standard sets down which values mean what, 1 so one site
could use writer for the same thing another site uses author for, or two
sites could use author to mean something completely different. This
isn't a huge issue, because HTML isn't intended to describe real-world
things like authors, so the meaning behind those values is likely to be
site-specific anyway. But id and class attributes can also be used to
describe document features; for instance, a nav class would probably
indicate an element that contains navigation. If you were looking for
ideas for new elements to add to HTML to improve its ability to
describe documents, a survey of the sorts of values used in id and class
attributes would be a good place to start.
With this in mind, in 2005 several studies were done that attempted to
analyze how authors were using id and class values in markup on the
web. Two of these are of particular interest to us:
In November 2005, a study of 1,315 websites counted how often dif-
ferent values for the id attribute were used.
In December 2005, a study of slightly over a billion web pages ana-
lyzed, among other things, how often particular class names
Although some have attempted it. See the discussion of microformats later in this chapter.
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