HTML and CSS Reference
In-Depth Information
web page using elements such as a div element with an id attribute. For example, pre-
viously a footer section might have been created with this:
<div id="footer">copyright 2011</div>
Using the new section tags, this could be rewritten as follows:
<footer>copyright 2011</footer>
Using these new structural tags is clearer and standardizes the identifier for this tag,
since an id attribute could be written “page-footer,” “thefooter,” and so on, by different
authors. The “Semantic Web” aims to provide clearly defined content that is readable
by machines for better data mining/search purposes. The old format makes it impossible
for a machine to pick out the footer consistently on several different web pages, while
the HTML5 syntax makes it totally predictable—assuming, of course, the author in fact
was using the footer tag for the appropriate section of their web page.
In addition to new structural elements, there have been major upgrades to the element
types available in web forms, introducing new input types for entering dates, URLs,
e-mail addresses, phone numbers, and so on. Also introduced is a number of new ele-
ments for embedded and interactive content, such as the video , audio , and canvas
(a scriptable drawing surface). There have also been changes to existing elements, such
as redefining the meaning (semantics) of the b , i , and small elements so that they are
no longer presentational in nature. The new elements and changes to existing elements
will be explored in greater detail in upcoming chapters.
This new addition is based on the idea of annotating HTML elements for the purposes
of adding metadata to the page's content so that it may more easily, and in a standardized
way, be processed by external applications, aggregators, and search engines. This idea
isn't new. Microformats and RDFa are two formats for annotating HTML for this pur-
pose, but HTML5 introduces a third format: Microdata (itself based on RDFa). Mi-
crodata uses a set of global attributes that may be used to add additional semantic struc-
ture to the content on a page.
Embedded MathML and SVG
Mathematical Markup Language (MathML) and Scalable Vector Graphics (SVG) are
both XML-based markup languages that are described in different specifications than
HTML. As the name implies, MathML is for describing and presenting math equations
using correct mathematical notation. SVG is used for describing interactive and static
(noninteractive) vector-based graphics. Neither of these languages is new, but since
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