Q:

What is the xml:lang attibute of XHTML 1.0 means?

Here is XHTML 1.0 Transitinal DTD:  
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" 
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title></title>
</head>
<body>

</body>
</html>

following the xml namespace attribute,can I change the xml:lang and lang to another value,such as other language?how it works?Thanks guys!

A:

The xml:lang attribute is simply the lang attribute that corresponds to XML itself (xml being its namespace). Since XHTML derives from XML, elements in an XHTML document must have the xml:lang attribute, along with the HTML lang attribute. You usually just declare xml:lang on the <html> opening tag and everything else inside will "inherit" the language value appropriately.
If you need to specify a different language, make sure to specify the same value for both attributes.
This is stated in the XHTML 1.0 spec:

Use both the lang and xml:lang attributes when specifying the language of an element. The value of the xml:lang attribute takes precedence.

