Only half size on mobile

Hi
I have a small wordpress site (with TwentyTwelve child theme)
On mobile some of the sites seems like only half size (and background showing rest)
See screendump here:
https://www.dropbox.com/s/0wvjs7gza012syf/wordpress.png?dl=0

Is it because of the image size ? or how can I fix it ?

Thanks

The page I need help with: [log in to see the link]