Web Development and Design Foundations with XHTML, 5th Edition

(^580) Appendix A XHTML Reference
declaration is recommended by the W3C to be the first line in a Web page document.
However, in practice, this line is omitted and, instead, a metatag that indicates
character encoding is typically coded in the header section of the Web page.
The DOCTYPE(DTD) Tag
The DOCTYPEor DTDtag identifies the markup language used in a document. Three
DTDs are valid in XHTML. They are listed in Table A.1.
The Ta g

The tag contains the code that describes the Web page document. The tag also
describes the location of the documentation for the elements being used (called the XML
namespace or xmlns). This additional information is added to the tag in the form
of an xmlnsattribute. The xmlnsattribute points to the URL of the XHTML namespace
used in the document, the standard “http://www.w3.org/1999/xhtml.” Optionally, you
can add attributes to specify the language of the document (for example, English is “en,”
German is “de”) to assist the interpreting of page content by search engines and screen
readers. The lang and xml:langattributes are used for this purpose. See [http://www.loc.](http://www.loc.)
gov/standards/iso639-2/php/English_list.php for a list of language codes. The tag
is the first tag in a Web page after the DOCTYPE tag. For example:
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

... the rest of your web page goes here ...

The Ta g

The tag is required and encloses the header area of a Web page document. The
main purpose of the header area is to describe the document. The header usually con-
tains