Speaking about the different types of HTML standards, a definition must be offered. Here come the DTD, which means Document Type Definition and, simply speaking, is a set of rules that defines the different versions of HTML and XHMTL on the net.
All the tags that are contained in a version of HTML are defined in its DTD, so the DTDs are like some dictionaries of all the possible tags in the markup language. It contains not only the HTML tags, but also what do they mean and how they are related one to another.
Practically, there are
"So What is a DTD?
The tags in the HTML language must be defined somewhere, right? They are defined in the DTD, which stands for Document Type Definition. In a DTD for HTML, all the HTML tags are defined. Everything is defined in the DTD -- the tags, the attributes, the possible values they can hold. Think of the DTD as the HTML tag dictionary: it lists all the tags, what they mean, and how they relate to each other.
Also, there are different DTDs because there are different versions of HTML:
HTML 4.01 Strict
HTML 4.01 Transitional
XHTML
Still writing your documents in HTML? If you are, you're not complying with current standards. On January 26, 2000, XHTML 1.0 became a recommendation by the World Wide Web Consortium (W3C). HTML, according to the W3C, is no longer the Web markup standard. Instead, XHTML 1.0 has replaced our old favorite, marking up the dawn of a new and exciting time in communications technology.
So what exactly is XHTML 1.0 and what does it mean to the Web developer? I'll start with the W3C's description: XHTML 1.0 is a reformulation of HTML as an XML application.
Still writing your documents in HTML? If you are, you're not complying with current standards. On January 26, 2000, XHTML 1.0 became a recommendation by the World Wide Web Consortium (W3C). HTML, according to the W3C, is no longer the Web markup standard. Instead, XHTML 1.0 has replaced our old favorite, marking up the dawn of a new and exciting time in communications technology.
So what exactly is XHTML 1.0 and what does it mean to the Web developer? I'll start with the W3C's description: XHTML 1.0 is a reformulation of HTML as an XML application.
This section of the specification describes the basic data types that may appear as an element's content or an attribute's value.
For introductory information about reading the HTML DTD, please consult the SGML tutorial.
1. Case information:
Each attribute definition includes information about the case-sensitivity of its values. The case information is presented with the following keys:
CS
The value is case-sensitive (i.e., user agents interpret "a" and "A" differently).
CI
The value is case-insensitive (i.e., user agents interpret "a"
RSS/XML