How to validate my HTML5 site?

From: Nikotine Lutritio <nikotine192@hotmail.com>
Date: Fri, 6 Nov 2015 15:32:43 +0100
To: "html-tidy@w3.org" <html-tidy@w3.org>
Message-ID: <DUB130-W80F843DBB52EE2BBF142CE0280@phx.gbl>

Hi there,
I am trying to validate my airline review website http://uk.whattheflight.com the corresponding validator but it does not seems to work.
Can anyone help?
Thank you 
Niko

Received on Friday, 6 November 2015 14:33:13 UTC