The prologue appears at the beginning of every HTML page, identifies what follows as an HTML document allowing browsers and other special software to distinguish HTML documents from other types (DTDs) of SGML. All HTML documents written according to the current HTML specification (Version 4.01) should use the prologue tag displayed below.
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" >
· HTML - The SGML document type being declared: <HTML> ... </HTML>
· PUBLIC - Identifies the information in quotes as a Formal PUBLIC Identifier.
· "-" - The minus sign designates unregistered organization. ISO, registered (+) or unregistered (-) are possible here. W3C is not currently registered with ISO, therefore the (-) is used.
· W3C - identifies the party responsible for creation/maintenance of the DTD. If the DTD comes from IETF, W3C, etc. you'll see their ID here.
· DTD - describes the type of object, called a Public Text Class. In this case, it is a DTD.
· HTML 4.01 Transitional - is the Public Text Description. Here you'll find the DTD's name, plus flavors such as version numbers, "strict", "draft," "transitional," etc.
EN - identifies the Public Text Language, describing the natural language in which the public text is written, represented by two, uppercase-only characters from ISO 639. "EN"= English.
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