Theme issue on ios devices

I had my wordpress site created by a “vendor” and since then I have taken over day to day administration. The other day I noticed that my page does not show up correctly on ios devices. The header and footer do not seem to stretch all the way to the right hand side.

I believe that the vendor customized the Twenty eleven theme and maybe there is a right side column but I do not know enough about wordpress to tell if the theme has a column or not.

So far its been tested on ipad and iphone. Works fine on Windows PCs and macs.

Thanks