XHTML Syntax

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Some 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

Attribute Names Must Be In Lower Case

This is wrong:

<table WIDTH="100%">

This is correct:

<table width="100%">

Attribute Values Must Be Quoted

This is wrong:

<table width=100%>

This is correct:

<table width="100%">

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"

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>

Mandatory XHTML Elements

All XHTML documents must have a DOCTYPE declaration. The html, head, title, and body elements must be present.

This is an XHTML document with a minimum of required tags:

<!DOCTYPE Doctype goes here>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Title goes here</title>
</head>

<body>
</body>

</html>

Note: The DOCTYPE declaration is not a part of the XHTML document itself. It is not an XHTML element. You will learn more about the XHTML DOCTYPE in the next chapter.

Note: The xmlns attribute in <html>, specifies the xml namespace for a document, and is required in XHTML documents. However, the HTML validator at w3.org does not complain when the xmlns attribute is missing. This is because the namespace "xmlns=http://www.w3.org/1999/xhtml" is default, and will be added to the <html> tag even If you do'nt include it.


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