XHTML 1.0: Where XML and HTML meet
How to ensure backwards compatibility?
Here are some design guidelines to follow for XHTML documents to
render correctly in existing HTML user agents.
- Properly format empty elements I
Include a space before the trailing / and > of empty elements, e.g. <br />, <hr /> and
<img src="photo.jpg" alt="Photo" />. Also, use the minimized tag syntax for empty elements,
e.g. <br />, as the alternative syntax <br></br> allowed by XML gives uncertain results
in many existing user agents.
- Properly format empty elements II
Given an empty instance of an element whose content model is not EMPTY (for example, an
empty title or paragraph) do not use the minimized form (e.g. use <p> </p> and
not <p />).
- Eliminate embedded Style Sheets and Scripts
Use external style sheets and scripts if they use < or & or ]]> or --.
XML parsers are permitted to silently remove the contents of comments,
so the historical practice of "hiding"
scripts and style sheets within comments to make the documents backward compatible is
likely to not work as expected in XML-based implementations.
- Avoid Line Breaks within Attribute Values
Avoid line breaks and multiple whitespace characters within attribute values. These are
handled inconsistently by user agents.
- Use only one isindex element
Don't include more than one isindex element in the document head.
It is deprecated in favor of the input element.
- Use the lang and xml:lang Attributes
Use both the lang and xml:lang attributes when specifying the
language of an element.
- Fix up Fragment Identifiers
In XML, URIs [RFC2396] that end with fragment identifiers of the form "#target" do not refer
to elements with an attribute name="target"; rather, they refer to elements with an attribute
defined to be of type ID, e.g., the id attribute in HTML 4. Many existing HTML clients
don't support the use of ID-type attributes in this way, so identical values may be
supplied for both of these attributes to ensure maximum forward and backward compatibility
(e.g., <a id="target" name="target">...</a>).
- Add the XML Character Encoding declaration
To specify a character encoding in the document, use both the encoding attribute
specification on the xml declaration (e.g. <?xml version="1.0" encoding="EUC-JP"?>) and a
meta http-equiv statement (e.g. <meta http-equiv="Content-type" content='text/html;
charset="EUC-JP"' >>).
- Use Ampersand entities in Attribute Values
When an attribute value contains an ampersand, it must be expressed as a character entity
reference (e.g. "&"). For example, when the href attribute of the
a element refers to a CGI script that takes parameters, it must be expressed as
NOT: http://webref.com/cgi-bin/xml/demo1.pl?style=none&name=user
BUT: http://webref.com/cgi-bin/xml/demo1.pl?style=none&name=user
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Produced by Michael Claßen
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URL: http://www.webreference.com/xml/column6/4.html
Created: Feb. 07, 2000
Revised: Feb. 07, 2000
