<!DOCTYPE html> is a a declaration that we use to inform the browser of any visitor that this document is an HTML document.
To be compliant with HTML standards, every HTML document should have DOCTYPE declaration.
<!DOCTYPE html> should always be placed at the top of your HTML document:
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8" /> <meta name="viewport" content="width=device-width, initial-scale=" /> <title></title> </head> <body></body> </html>
It's as simple as that!