Hi Dave,
I see two problems happening, one is that the menu on your 'clients.html' page has a link to 'Clients.html' (with an uppercase 'C') - this needs to be a lowercase 'c'.
The second thing is that there doesn't appear to be a 'contact.html' file in your /ai/ directory on the remote server. Check that the page is there, and that it is called exactly 'contact.html'.
Everything else seems OK from here.