menu navigation issues with mobile browsers

Hi, I'm having some issues with access the menu links on mobile devices. I currently have only two links for Home (default) and an About page. I don't have an Android or iOS smartphone to test on but for those that I have sometimes from the home page selecting the About link doesn't function and it all cases once in a particular post page the About link doesn't function for any of them. I have checked the Catch Box preview http://catchthemes.com/preview/?theme=catchbox on one of the devices and while the last item in the upper navigation "HTML Elements" appears first I don't notice any immediate navigation related issues so I was wondering that given that I have added custom CSS to reduce the spacing in the header area so I was wondering has that perhaps broken something?