What is the new DOCTYPE?
 

Formally, in SGML and XML, a DOCTYPE announcement is a reference to a Document Type Definition (DTD), which determines the formal sentence structure principles of the markup dialect. No program has ever utilized DTDs for anything or even got to them.

The Doctype stuff that is there tells the browser how to read the HTML. You will typically see strict 1.0 ones used in email, due to emails clients. is HTML 5.

The declaration is not an HTML tag; it is an instruction to the web browser about what version of HTML the page is written in. In HTML 4.01, the declaration refers to a DTD, because HTML 4.01 was based on SGML. ... HTML5 is not based on SGML, and therefore does not require a reference to a DTD.

The declaration is not an HTML tag; it is an instruction to the web browser about what version of HTML the page is written in. In HTML 4.01, the declaration refers to a DTD, because HTML 4.01 was based on SGML.