Marks beginning of HTML document. Contains info about the page. Title of the page. Marks beginning of content. Heading tags range from the biggest H1 to the smallest, H6.
Marks end of content.
Marks end of HTML document. They do not recognize tabs. You can include as much white space as you like in a Web page. It has no effect whatsoever on the way the page looks in a browser. Include white space to make your page easy to read.