PUBLIC MARKS with tags dtd & doctype

In order to deal with both old tag soup written to old browser quirks and new CSS-compliant pages, Firefox (and other Mozilla Gecko-based browsers), Safari, Opera (7 and later), Internet Explorer 6 and 7, Mac IE 5, and Konqueror (3.2 and later) have two main layout modes. In one mode the layout engine attempts to render conforming pages according the CSS specifications. In the other mode the layout engine tries to mimic old browsers. In Firefox these modes are known as “the Standards mode” and “the Quirks mode” respectively. In this document the same names are used also when referring to the modes of the other browsers.

Listado de DOCTYPES desde la página de la W3C

Cette page web permet de comprendre l'intérêt de choisir le bon type de doctype en tête de page HTML et pourquoi les pages ne s'affichent pas de la même manière d'un navigateur à l'autre.