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[html] 31.HTML5 为什么只需要写 <!DOCTYPE HTML>？ #52

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qiilee opened this issue Sep 29, 2019 · 0 comments
Open

[html] 31.HTML5 为什么只需要写 <!DOCTYPE HTML>？ #52

qiilee opened this issue Sep 29, 2019 · 0 comments
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qiilee commented Sep 29, 2019

答案：HTML 4.01 中的 doctype 需要对 DTD 进行引用，因为 HTML 4.01 基于 SGML。而 HTML 5 不基于 SGML，因此不需要对 DTD 进行引用，但是需要 doctype 来规范浏览器的行为。其中，SGML 是标准通用标记语言,简单的说，就是比 HTML,XML 更老的标准，这两者都是由 SGML 发展而来的。BUT，HTML5 不是的。

<!DOCTYPE>声明位于位于 HTML 文档中的第一行，处于 <html> 标签之前。作用：告知浏览器的解析器用什么文档标准解析这个文档。DOCTYPE 不存在或格式不正确会导致文档以怪异模式呈现。
@qiilee qiilee added the HTML label Sep 29, 2019
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