500 Can't connect to www.peepo.com:80 (Bad hostname 'www.peepo.com')

here:  http://validator.w3.org/check?uri=http://www.peepo.com

i get the message:

I got the following unexpected response when trying to retrieve 
<http://www.peepo.com/>:


500 Can't connect to www.peepo.com:80 (Bad hostname 'www.peepo.com')


Please make sure you have entered the URI correctly.

--

Please note: if you click on the link peepo is available.
Not sure why this is happening, but I'd like to be able to use this 
service please.

Can you please tell me what needs to be done?

thanks

Jonathan