html中doctype的内容

sap*_*Pro 0 html doctype

我不明白html中的doctype.

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
 "http://www.w3.org/TR/html4/strict.dtd">
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你能解释一下这里的每件事是什么意思吗?

Ode*_*ded 6

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN"
            "http://www.w3.org/TR/html4/strict.dtd">


!DOCTYPE - The document type declaration
HTML - The root element is HTML, the type of document is HTML
PUBLIC - Availability - this is a public doctype
"-//W3C//DTD HTML 4.01//EN" - A formal identifier
"http://www.w3.org/TR/html4/strict.dtd" - URI, here it is the location of the DTD
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about.com上有进一步细分.