What's the purpose of HTMl doctype's .dtd? -


when @ xhtml doctype, there's .dtd file.

<!doctype html public "-//w3c//dtd xhtml 1.0 transitional//en" "http://www.w3.org/tr/xhtml1/dtd/xhtml1-transitional.dtd">

what's purpose of it?

do browsers access , use parse html?

if so, happens when w3.org goes down?

the document type definition there tell browser version of html being used. dates sgml (standard generalised markup language). sgml used explain browser how understand structure of document (such html page). interestingly enough, xml restricted subset of sgml many (exotic) features turned off.

browsers use parse document don't need nuke w3c servers request every time document fetched. instead use cached local copy.

when w3c.org goes down, continue use cached copy. unless specify url of course...

one more thing note regard doctype declaration is gone in html5, because html5 no longer based on sgml. html5 uses <!doctype html>.


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