First in this article, I'll correct the mistake before I write the introductory article, still quote is the official version first, avoid misleading novice you again

<! DOCTYPE> Statement must be in the first line in HTML5 document, which is located in <Html> Before the tag. This tag tells the browser document used by the HTML specification.

the doctype declaration is not HTML tags; The tag; It is an instruction that tells the browser page write the markup version.

on all HTML documents stipulated in the doctype is very important, so that the browser can know the desired document type.

4.01 HTML doctype in the referenced to DTD, because HTML 4.01 based on SGML. And HTML 5 is not based on SGML and therefore do not need a DTD for reference, but need a doctype to regulate the behavior of the browser, the browser should according to their way to run.) .

in the HTML 4.01 there are three different document types, there is only one in HTML 5:

<! DOCTYPE html> Because HTML5

the statement document type label is downward compatible, so even if your HTML is basic does not use HTML5 tags, you can also use the declarative way, but the page where there will be some incompatible, it need you revised according to actual situation. <! DOCTYPE html> Can let the browser renders pages under strict mode (standard model), and do not need to specify a type DTD.

to enter today's subject: table and reasonable application of div

This concludes the body part