What is the meaning of <!DOCTYPE>?
This is not an html tag. The <!DOCTYPE> syntax should be the first thing in HTML page, before the <html> tag. It is an instruction to the web browser about what version of HTML the page is written in. In HTML 4 we used <!DOCTYPE HTML PUBLIC ‘-//W3C//DTD HTML 4.01//EN’ ‘http://www.w3.org/TR/html4/strict.dtd’> But now in HTML 5 we used only <!DOCTYPE html>