css2
At Bellevue College - The Doctype

The <!DOCTYPE> declaration must be the very first thing in your HTML document, before the <html> tag. The <!DOCTYPE> declaration is not an HTML tag; it is an instruction to the web browser about what version of HTML the page is written in.

And... here it is!

XHTML Transitional

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"https://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="https://www.w3.org/1999/xhtml">

<head>

<title>Title of document</title>

</head>

<body>

......

</body>

</html>

XHTML Strict

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "https://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="https://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<title>Untitled Document</title>
</head>

<body>
</body>
</html>

HTML 4

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "https://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Untitled Document</title>
</head>

<body>
</body>
</html>

HTML 5

<!doctype html>
<html>
<head>
<meta charset="UTF-8">
<title>Untitled Document</title>

<!-- Remy Sharp Shim -->
<!-- [if lt IE 9]>
<script src="https://html5shiv.googlecode.com/svn/trunk/html5.js">
</script>
<![endif]-->

</head>

<body>
</body>
</html>