HTML Documents: Omitting <html>, <head> and <body>

//the following code will validate as HTML5

<!DOCTYPE html>
<title>Page Title</title>

<h1>This is a heading</h1>
<p>This is a paragraph.</p>

According to the HTML5 standard; the <html>, the <body>, and the <head> tag can be omitted.

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Omitting <html>, <head> and <body>

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