HTML and CSS Reference
In-Depth Information
figure 9-14
HtML5 vs. XHtML
Syntax Issue
HTML5
XHTML
Attribute minimization
Attributes need not have attribute
values.
All attributes must have attribute
values.
Attribute names
Attribute names are not case
sensitive.
Attribute names must be
lowercase.
Attribute values
Unquoted attribute values are
allowed.
All attribute values must be
enclosed in quotes.
DOCTYPE
A DOCTYPE is required in the form
<!DOCTYPE html >
The DOCTYPE is optional.
Element names
Element names are not case
sensitive.
Element names must be lowercase.
Empty element tags
A closing slash may or may not be
used with an empty element tag.
Empty element tags must include
a closing slash.
Error validation
In HTML5 there are no well-
formedness constraints; no errors
are fatal.
Well-formedness errors are fatal.
Namespace prefixes
Namespace prefixes are not sup-
ported in HTML5.
Namespace prefixes are supported
in XHTML.
Namespaces
Elements and attributes for known
vocabularies (HTML, SVG, and
MathML) are implicitly assigned.
Namespaces must be explic-
itly declared using the
xmlns
attribute.
Processing instructions
HTML5 does not support process-
ing instructions and instead treats
the enclosed text as a comment.
Allows the use of processing
instructions closed with
ƒ?>
The rules for HTML5 are much more open than for XHTML. For example, an HTML5
document is considered valid regardless of whether attributes have attribute values,
whether attribute names and element names are in lowercase letters, or whether empty
element tags have closing slashes. Even though HTML5 does not have the same syntax
requirements as XHTML, you should follow the general XHTML syntax rules in case you
need to work with XHTML or XML documents in the future.
Note that with XHTML, you cannot use the HTML5 structural elements including the
header
,
footer
,
nav
,
section
,
article
,
aside
,
hgroup
,
figure
, and
figcaption
elements. One alternative to using those elements is to use
div
elements, and identify
the purpose of each
div
element using an
id
attribute. Thus, under XHTML, you can use
the following
div
element to make a page header:
<divƒid=”header”>ƒ…ƒ</div>
However, there is no specification in XHTML to use one id value over another. A
different author might use an id value of
head
or
title
. Syntactical elements such as the
header
element are one of the chief advantages of HTML5 in that they provide a com-
mon structure for Web pages.
