Visual Basic.NET How to Program (PDF)

Appendix J Introduction to XHTML: Part 1 1403
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10 Visual Basic .NET How to Program - Welcome
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14 Welcome to XHTML!
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Fig. J.1 First XHTML example (part 2 of 2).
XHTML markup contains text that represents the content of a document and elements
that specify a document’s structure. Some important elements of an XHTML document
include the html element, the head element and the body element. The html element
encloses the head section (represented by the head element) and the body section (represented
by the body element). The head section contains information about the XHTML
document, such as the title of the document. The head section also can contain special document
formatting instructions called style sheets and client-side programs called scripts for
creating dynamic Web pages. The body section contains the page’s content that the browser
displays when the user visits the Web page.
XHTML documents delimit an element with start and end tags. A start tag consists of
the element name in angle brackets (e.g., ). An end tag consists of the element
name preceded by a / in angle brackets (e.g., ). In this example, lines 8 and 16
define the start and end of the html element. Note that the end tag on line 16 has the same
name as the start tag, but is preceded by a / inside the angle brackets. Many start tags define
attributes that provide additional information about an element. Browsers can use this additional
information to determine how to process the element. Each attribute has a name and
a value separated by an equal sign (=). Line 8 specifies a required attribute (xmlns) and
value (http://www.w3.org/1999/xhtml) for the html element in an XHTML
document. For now, simply copy and paste the html element start tag on line 8 into your
XHTML documents. We discuss the details of the html element’s xmlns attribute in
Chapter 18, Extensible Markup Language (XML).
Common Programming Error J.1
Not enclosing attribute values in either single or double quotes is a syntax error. J.1
Common Programming Error J.2
Using uppercase letters in an XHTML element or attribute name is a syntax error. J.2