The document type tag, the first line in your page.
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/REC-html40/loose.dtd">.
<html> - starts and ends every page.
<head> - contains information about the page.
<title> - provides a title displayed in the title bar of the page.