Check the headers.
The header is not what defines which version of HTML a web document uses.
It's the DOCTYPE. In the case of this page, it is declared as HTML 4.0 Transitional. (See: HTML Declaration)
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
For a web document to be declared HTML 5, the DOCTYPE needs to be:
<!DOCTYPE html>
Hey, I’m an outboard mechanic and hardware salesman, not a GEEK!