Website layout problem on iPad mini

I’ve checked the website on my tablets and found an issue with the layout on my iPad mini.

If I view the page in landscape mode in Safari, there is no problem. But if I view the page in portrait mode, the page doesn’t resize properly and I can only view the sidebar.

Any ideas of how I can fix this? I had no problem viewing the page on my Samsung Galaxy Tab in either mode.

The page is here: http://ossan-girl.com/about-og/

You’ll also notice there’s an issue with the Disqus comment, but that’s being worked on with their support team at the moment.

Many thanks in advance!