12.3. Keep the Quirks: DOCTYPE Switching

Web pages that are coded to display in earlier browsers (versions that don't offer full CSS support) may look ugly, or fail to display at all in later browsers that do support CSS. Badly formed HTML, which earlier browsers forgave, breaks in newer browsers that must render HTML more meticulously because of the strict rules that come with standards like CSS.

The opposite is also true, as we've seen. Pages designed to display well in recent and new browsers may not display well, or may fail to display at all, in older browsers. IE5 for Macintosh, IE6 for Windows, Netscape 6, and Mozilla browsers support a technology called DOCTYPE Switching. Simply stated, this technology allows these browsers to adapt ...

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