Specification
A great resource you should bookmark and use:
View -> Developer -> View Source
Option + Cmd + U
Type in the following:
<!DOCTYPE html> <html> <head> <title> The Title of this HTML Page </title> </head> <body> This is the body of this HTML Page </body> </html>
File -> Open File
<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8"> <title> The Title of this HTML Page </title> </head> <body> This is the body of this HTML Page </body> </html>The area in red is required to pass the strictist HTML specification