<!DOCTYPE html>
The <!DOCTYPE> declaration is not an HTML tag
The DTD specifies the rules for the markup language, so that
the browsers render the content correctly.
Tip: Always add the <!DOCTYPE> declaration to your HTML documents, so
that the browser knows what type of document to expect.
HTML 4.01 Strict
This DTD contains all HTML elements and attributes, but does NOT
INCLUDE presentational or deprecated elements (like font). Framesets are
not allowed.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
HTML 4.01 Transitional
This DTD contains all HTML elements and attributes, INCLUDING
presentational and deprecated elements (like font). Framesets are not
allowed.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
FAQ : What is DTD?
A DTD defines the structure and the legal elements and attributes of an XML document.
With a DTD, independent groups of people can agree on a standard DTD for interchanging data.
An application can use a DTD to verify that XML data is valid.
<!DOCTYPE note SYSTEM "note.dtd">
<note>
<to>Tove</to>
<from>Jani</from>
<heading>Reminder</heading>
<body>Don't forget me this weekend!</body>
</note>
Seen from a DTD point of view, all XML documents are made up by the following building blocks:
- Elements
- Attributes
- Entities
- PCDATA
- CDATA
Elements
Elements are the
main building blocks of both XML and HTML documents.
Examples of HTML elements are "body" and "table".
Examples of XML elements could be
"note" and "message".
<body>some text</body>
<message>some text</message>
Entities
Some characters have a special meaning in XML, like the less than sign (<)
that defines the start of an XML tag.
PCDATA
PCDATA means parsed character data.
Think of character data as the text found between the start tag and the end tag of an XML element.
CDATA
CDATA means character data.
CDATA is text that will NOT be parsed by a parser.
Tags inside the text will NOT be treated as markup and entities will not be expanded.
