What is <!DOCTYPE> tag ?
HTML <!DOCTYPE> tag is used to inform the browser about the version of HTML used in the document. It is called the Document Type Declaration (DTD).
Although it is not a tag/element, whereas it is just an instruction to the browser about the document type.
<!DOCTYPE html> <html> <head> <title>This is the title</title> </head> <body> This is the content of the document. </body> </html>