Help needed making menu resize for mobile

Hi

Having an issue with the following test site page:
http://willhutchinson.co.uk/pf-test/pages/pages-overview/paul-farrell-jessie.html

It works fine on desktop, but, unlike the main index page (below) the menu does not automatically resize when viewed on a mobile device.
http://willhutchinson.co.uk/pf-test/index.html

I'm guessing it is something buried in the CSS attached to the page, but I can't work it out.

It's probably simple and very possibly something very stupid I'm doing.

Any help or advice including alternate methods to get the same result, very much appreciated.

Cheers
Will

I looked at the page, a pretty simple fix would be to add platform specific code. Also, have you validated?