revision:
The <html> tag represents the root of an HTML document. The tag is the container for all other HTML elements (except for the <!DOCTYPE> tag). You should always include the "lang" attribute inside the <html> tag, to declare the language of the Web page. This is meant to assist search engines and browsers. Before the <html> tag we can only use <Doctype> declaration, which gives information about the HTML version to the browser.
<html> . . . </html>
Codes:
<html lang="en">
<head>
<title>Title of the document</title>
</head>
<body>
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>
Codes:
<!DOCTYPE html>
<html>
<head>
<title>HTML tag</title>
</head>
<body>
<h2>Example of HTML tag</h2>
<p> Write your main Content within Body of the HTML document. </p>
</body>
</html>