ARCHIVED - Document Type Definition
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Table of Contents
1.0 Introduction
In order to produce valid CLF compliant Web pages, the Document
Type Definition (DTD) must be declared at the beginning of each Web page. Each Web page must be designed with the full DOCTYPE declaration, so that Web devices
(such as browsers and PDAs) can render the Web pages correctly.
2.0 DOCTYPE switching
Consistent browser support for W3C recommendations (such as HTML and XHTML) had not yet been established when the recommendations were first introduced. At that time developers were forced to produce Web pages that were non-conformant with W3C recommendations for them to render correctly across various platforms.
DOCTYPE switching was introduced to enable support for Web pages that are conformant to W3C recommendations without breaking support for pages that had already been developed using non-conformant approaches. In general, DOCTYPE switching involves two display modes: Quirks
mode and Standards mode.
2.1 Quirks mode
Quirks mode was introduced to ensure support for Web pages that are non-conformant with W3C recommendations. Pages are normally rendered in Quirks mode when the full DTD is not provided at the beginning of the page.
Pages rendered in Quirks mode may vary significantly from browser to browser as the visual appearance is based upon each browser's interpretation of how the page was meant to be displayed.
2.2 Standards mode
Standards mode was introduced to enable support for Web pages that are conformant with W3C recommendations. Pages are normally rendered in Standards mode when the full DTD is provided at the beginning of the page.
Pages rendered in Standards mode tend to be consistent from browser to browser as the visual appearance is based upon W3C recommendations.
3.0 Valid Document Type Definitions
| W3C Recommendation | Compliant with CLF 2.0? | Code |
|---|---|---|
| HTML5 | Yes | <!DOCTYPE html> |
| XHTML 1.0 Strict | Yes | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" |
| XHTML 1.0 Frameset | Yes | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" |
| XHTML 1.0 Transitional | No | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" |
| HTML 4.01 Strict | No | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" |
| HTML 4.01 Frameset | No | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" |
| HTML 4.01 Transitional | No | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" |