DOCTYPE tags in HTML documents

when we write HTML pages, we usually add 〈!DOCTYPE〉 them in the first line. the tags, some editors will automatically help us to add, today talk about this 〈!DOCTYPE〉 the role of the label.

HTML and XHTML

W3Cbefore the organization also issued HTML standards, the development of the Web page when everyone did not add this tag, that time. HTML page development is also confusing, until 1999, HTML 4.01 became the recommended standard, when most people use this version. And probably in 2000, the organization also issued an XML version based on HTML4.01, named XHTML1.0.

The main difference between the two is that XHTML follows the encoding standard of XML, which means that the attributes of the added tag in the XHTML document must be included in "" , and all tags must be closed, and so on more stringent rules. This is also an experienced developer who often reminds new handwriting. html page to be aware of the place. Okay, here's the question:

• We mentioned earlier that when HTML 4.01 is not used as a recommendation, the HTML document is not 〈!DOCTYPE〉 labeled, and the browser faces an. html document, and if the tag is parsed, there is no explanation for the document.
• After the introduction of the standard, there are two versions (standard) to write. HTML documents, which standard should the browser use when parsing HTML documents?