Table of Contents
常用的 DOCTYPE 声明
HTML 5
HTML 4.01 Strict
HTML 4.01 Transitional
HTML 4.01 Frameset
XHTML 1.0 Strict
XHTML 1.0 Transitional
XHTML 1.0 Frameset
Home Web Front-end HTML Tutorial HTML头部声明文件类型_html/css_WEB-ITnose

HTML头部声明文件类型_html/css_WEB-ITnose

Jun 24, 2016 am 11:20 AM

在你每一个页面的顶端,你需要文件声明。是的,必须。

  如果不指定文件类型,你的HTML不是合法的HTML,并且大部分浏览器会用“怪癖模式(quirks mode)”来处理页面,这意味着浏览器认为你自己也不知道究竟做什么,并且按浏览器自己的方式来处理你的代码。你能是个HTML大师,在地球上打遍天下无敌手,或你的HTML能无瑕疵,CSS能非常完美,但如果没有文件声明,或错误的文件声明,你的网页和一个短视的,独眼的长臂猿婴儿十分艰难地堆砌起来的没两样。

      要想写出跨浏览器的CSS,必须知道浏览器解析CSS的两种模式:标准模式(strict mode)和怪异模式(quirks mode)。
所谓的标准模式是指,浏览器按W3C标准解析执行代码;怪异模式则是使用浏览器自己的方式解析执行代码,因为不同浏览器解析执行的方式不一样,所以我们称之为怪异模式。浏览器解析时到底使用标准模式还是怪异模式,与你网页中的DTD声明直接相关,DTD声明定义了标准文档的类型(标准模式解析)文档类型,会使浏览器使用相应的方式加载网页并显示,忽略DTD声明,将使网页进入怪异模式(quirks mode)。

  标准模式中IE6不认识!important声明,IE7、IE8、Firefox、Chrome等浏览器认识;而在怪异模式中,IE6/7/8都不认识!important声明,这只是区别的一种,还有很多其它区别。所以,要想写出跨浏览器的CSS,你必须采用标准模式。好像太绝对了,呵呵。好吧,要想写出跨浏览器CSS,你最好采用标准模式。

常用的 DOCTYPE 声明

HTML 5

<!DOCTYPE html>
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HTML 4.01 Strict

该 DTD 包含所有 HTML 元素和属性,但不包括展示性的和弃用的元素(比如 font)。不允许框架集(Framesets)。

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

该 DTD 包含所有 HTML 元素和属性,包括展示性的和弃用的元素(比如 font)。不允许框架集(Framesets)。

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

该 DTD 等同于 HTML 4.01 Transitional,但允许框架集内容。

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">
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XHTML 1.0 Strict

该 DTD 包含所有 HTML 元素和属性,但不包括展示性的和弃用的元素(比如 font)。不允许框架集(Framesets)。必须以格式正确的 XML 来编写标记。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
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XHTML 1.0 Transitional

该 DTD 包含所有 HTML 元素和属性,包括展示性的和弃用的元素(比如 font)。不允许框架集(Framesets)。必须以格式正确的 XML 来编写标记。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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XHTML 1.0 Frameset

该 DTD 等同于 XHTML 1.0 Transitional,但允许框架集内容。

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">
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