Tags and Attributes
For the most part, tags — the markup
elements of HTML and XHTML — are simple to understand and use,
since they are made up of common words, abbreviations, and notations.
For instance, the <i> and
</i> tags respectively tell the browser to
start and stop italicizing the text characters that come between
them. Accordingly, the syllable
“simp” in our barebones example
above would appear italicized on a browser display.
The HTML and XHTML standards and their various extensions define how and where you place tags within a document. Let’s take a closer look at that syntactic sugar that holds together all documents.
The Syntax of a Tag
Every
tag consists of a tag
name, sometimes followed by an optional list of
tag attributes, all placed between opening and
closing brackets (< and
>). The simplest tag is nothing more than a
name appropriately enclosed in brackets, such as
<head> and <i>.
More complicated tags contain one or more
attributes, which specify or modify the behavior
of the tag.
According to the HTML standard, tag and attribute names are not
case-sensitive. There’s no difference in effect
between <head>,
<Head>, <HEAD>, or
even <HeaD>; they are all equivalent. With
XHTML, case is important: all current standard
tag and attribute names are in lowercase.
For both HTML and XHTML, the values that you assign to a particular attribute may be case-sensitive, depending on your browser and server. In particular, file location and name references — or uniform resource ...
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