How to validate my HTML5 site?

From: Nikotine Lutritio <nikotine192@hotmail.com>
Date: Thu, 5 Nov 2015 21:46:27 +0100
To: "html-tidy@w3.org" <html-tidy@w3.org>
Message-ID: <DUB130-W454183AA0CB41890D5FDDE0290@phx.gbl>

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

Received on Friday, 6 November 2015 08:31:30 UTC