XHTML Syntax

More XHTML Syntax Rules

• Attribute names must be in lower case
• Attribute values must be quoted
• Attribute minimization is forbidden
• The XHTML DTD defines mandatory elements

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Attribute Names Must Be In Lower Case

This is wrong:

<table WIDTH="100%">

This is correct:

<table width="100%">

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Attribute Values Must Be Quoted

This is wrong:

<table width=100%>

This is correct:

<table width="100%">

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Attribute Minimization Is Forbidden

This is wrong:

<input checked> <input readonly> <input disabled> <option selected> <frame noresize>

This is correct:

<input checked="checked" /> <input readonly="readonly" /> <input disabled="disabled" /> <option selected="selected" /> <frame noresize="noresize" />

Here is a list of the minimized attributes in HTML and how they should be written in XHTML:

HTML	XHTML
compact	compact="compact"
checked	checked="checked"
declare	declare="declare"
readonly	readonly="readonly"
disabled	disabled="disabled"
selected	selected="selected"
defer	defer="defer"
ismap	ismap="ismap"
nohref	nohref="nohref"
noshade	noshade="noshade"
nowrap	nowrap="nowrap"
multiple	multiple="multiple"
noresize	noresize="noresize"

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The Lang Attribute

The lang attribute applies to almost every XHTML element. It specifies the language of the content within an element.
If you use the lang attribute in an element, you must also add the xml:lang attribute, like this:

<div lang="it" xml:lang="it">Ciao bella!</div>

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Mandatory XHTML Elements

An XHTML document must have a DOCTYPE declaration.
The html, head, title, and body elements must also be present.