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2.3 Embedded Tags
You probably noticed right away, perhaps in
surprise, that the browser displays less than half of the example
source text. Closer inspection of the source reveals that
what's missing is everything that's
bracketed inside a pair of less-than (<) and
greater-than (>) characters. [Section 3.3.1]
HTML and XHTML are embedded languages: you insert their directions,
or tags, into the same document that you and
your readers load into a browser to view. The browser uses the
information inside those tags to decide how to display or otherwise
treat the subsequent contents of your document.
For instance, the <i> tag that follows the
word "Hello" in the simple example
tells the browser to display the following text in italics.Section 4.5]
[1] Italicized text is a very simple example and one that most
browsers, except the text-only variety (e.g.,
Lynx), can handle. In general, the
browser tries to do as it is told, but as we demonstrate in upcoming
chapters, browsers vary from computer to computer and from user to
user, as do the fonts that are available and selected by the user for
viewing HTML documents. Assume that not all are capable or willing to
display your HTML document exactly as it appears on your
screen.
The first word in a tag is its formal name, which usually is fairly
descriptive of its function, too. Any additional words in a tag are
special attributes, sometimes with an associated
value after an equals sign (=), which further
define or modify the tag's actions.
2.3.1 Start and End Tags
Most tags define and affect a discrete
region of your document. The region begins where the tag and its
attributes first appear in the source document (a.k.a. the
start tag ) and continues until a corresponding
end tag. An end tag is the
tag's name preceded by a forward slash
(/ ). For example, the end tag that matches the
"start italicizing"
<i> tag is </i>.
End tags never include attributes. In HTML, most tags, but not all,
have an end tag. And, to make life a bit easier for HTML authors, the
browser software often infers an end tag from surrounding and obvious
context, so you needn't explicitly include some end
tags in your source HTML document. (We tell you which are optional
and which are never omitted when we describe each tag in later
chapters.) Our simple example is missing an end tag that is so
commonly inferred and hence not included in the source that some
veteran HTML authors don't even know that it exists.
Which one?
The XHTML standard is much more rigid, insisting that all tags have
corresponding end tags. [Section 16.3.2] [Section 16.3.3]
